diff --git a/GUI/Model/Project/ID.h b/GUI/Model/Project/ID.h
deleted file mode 100644
index 4b9a6dd8c030a5916b8c76ccc3b423a420e37751..0000000000000000000000000000000000000000
--- a/GUI/Model/Project/ID.h
+++ /dev/null
@@ -1,25 +0,0 @@
-//  ************************************************************************************************
-//
-//  BornAgain: simulate and fit reflection and scattering
-//
-//! @file      GUI/Model/Project/ID.h
-//! @brief     Defines shared enums.
-//!
-//! @homepage  http://www.bornagainproject.org
-//! @license   GNU General Public License v3 or higher (see COPYING)
-//! @copyright Forschungszentrum Jülich GmbH 2023
-//! @authors   Scientific Computing Group at MLZ (see CITATION, AUTHORS)
-//
-//  ************************************************************************************************
-
-#ifndef BORNAGAIN_GUI_MODEL_PROJECT_ID_H
-#define BORNAGAIN_GUI_MODEL_PROJECT_ID_H
-
-namespace GUI {
-
-//! Which distributions should be available in the selector
-enum class DistributionsCategory { All, Symmetric };
-
-} // namespace GUI
-
-#endif // BORNAGAIN_GUI_MODEL_PROJECT_ID_H
diff --git a/GUI/Model/Project/ProjectDocument.cpp b/GUI/Model/Project/ProjectDocument.cpp
index b1560bddd0df4dda4257285f81b5dec54508d301..b1514a6b270daabb0c6a6c2ca7196d7b0aa2b051 100644
--- a/GUI/Model/Project/ProjectDocument.cpp
+++ b/GUI/Model/Project/ProjectDocument.cpp
@@ -17,7 +17,6 @@
 #include "GUI/Model/File/DatafilesSet.h"
 #include "GUI/Model/Job/JobsSet.h"
 #include "GUI/Model/Material/MaterialItem.h"
-#include "GUI/Model/Project/ID.h"
 #include "GUI/Model/Project/ProjectUtil.h"
 #include "GUI/Model/Sample/ItemWithMaterial.h"
 #include "GUI/Model/Sample/SamplesSet.h"
diff --git a/GUI/View/Device/AlphaScanEditor.cpp b/GUI/View/Device/AlphaScanEditor.cpp
index f3f472c57a4b4f71a0ae41fd0d656ec3c8db53ad..39990a5707116d47b38e84a91d260dbb8947dff5 100644
--- a/GUI/View/Device/AlphaScanEditor.cpp
+++ b/GUI/View/Device/AlphaScanEditor.cpp
@@ -38,7 +38,7 @@ AlphaScanEditor::AlphaScanEditor(QWidget* parent, GrazingScanItem* item, bool al
     connect(m_form, &SphericalAxisForm::dataChanged, this, &AlphaScanEditor::dataChanged);
 
     //... beam distribution
-    m_selector = new DistributionSelector(std::nullopt, GUI::DistributionsCategory::Symmetric, this,
+    m_selector = new DistributionSelector(std::nullopt, DistributionSelector::DistributionsCategory::Symmetric, this,
                                           m_item, allow_distr);
     connect(m_selector, &DistributionSelector::distributionChanged, this,
             &AlphaScanEditor::dataChanged);
diff --git a/GUI/View/Device/DistributionEditor.cpp b/GUI/View/Device/DistributionEditor.cpp
index bb2b23ac7b625d5ad0f3cac4f7104f550efc4436..f68ff53f983e2cd55270932f4ce34b6661287e74 100644
--- a/GUI/View/Device/DistributionEditor.cpp
+++ b/GUI/View/Device/DistributionEditor.cpp
@@ -19,7 +19,8 @@
 
 DistributionEditor::DistributionEditor(const QString& title,
                                        const std::optional<MeanConfig>& mean_config,
-                                       GUI::DistributionsCategory distributions, QWidget* parent,
+                                       DistributionSelector::DistributionsCategory distributions,
+				       QWidget* parent,
                                        BeamDistributionItem* item, bool allow_distr)
     : StaticGroupBox(title, parent)
     , m_selector(new DistributionSelector(mean_config, distributions, this, item, allow_distr))
diff --git a/GUI/View/Device/DistributionEditor.h b/GUI/View/Device/DistributionEditor.h
index cc0c1df5b3bf60545857e93acf1604ae5e08c98c..b7fad8f750a87af828827d2cd61db5075573b496 100644
--- a/GUI/View/Device/DistributionEditor.h
+++ b/GUI/View/Device/DistributionEditor.h
@@ -15,8 +15,7 @@
 #ifndef BORNAGAIN_GUI_VIEW_DEVICE_DISTRIBUTIONEDITOR_H
 #define BORNAGAIN_GUI_VIEW_DEVICE_DISTRIBUTIONEDITOR_H
 
-#include "GUI/Model/Project/ID.h"
-#include "GUI/View/Device/DistributionSelector.h" // MeanConfig
+#include "GUI/View/Device/DistributionSelector.h" // MeanConfig, DistributionsCategory
 #include "GUI/View/Widget/GroupBoxes.h"
 #include <optional>
 
@@ -30,7 +29,7 @@ class DistributionEditor : public StaticGroupBox {
     Q_OBJECT
 public:
     DistributionEditor(const QString& title, const std::optional<MeanConfig>& mean_config,
-                       GUI::DistributionsCategory distributions, QWidget* parent,
+                       DistributionSelector::DistributionsCategory distributions, QWidget* parent,
                        BeamDistributionItem* item, bool allow_distr = true);
 
     //! Update UI from data
diff --git a/GUI/View/Device/DistributionSelector.cpp b/GUI/View/Device/DistributionSelector.cpp
index ac53c6beebab0360ffbc0da5ab37b6660aec2fce..ec512f375531af288c087834f0c1efea37b74ee6 100644
--- a/GUI/View/Device/DistributionSelector.cpp
+++ b/GUI/View/Device/DistributionSelector.cpp
@@ -22,7 +22,7 @@
 #include "GUI/View/Numeric/NumWidgetUtil.h"
 
 DistributionSelector::DistributionSelector(std::optional<MeanConfig> mean_config,
-                                           GUI::DistributionsCategory distributions,
+                                           DistributionsCategory distributions,
                                            QWidget* parent, BeamDistributionItem* item,
                                            bool allow_distr)
     : QWidget(parent)
diff --git a/GUI/View/Device/DistributionSelector.h b/GUI/View/Device/DistributionSelector.h
index f9974003c3e34df8915cad850fcf197d59ef4dd6..98b7451202079178c344a321d93123a80c202fa6 100644
--- a/GUI/View/Device/DistributionSelector.h
+++ b/GUI/View/Device/DistributionSelector.h
@@ -15,7 +15,6 @@
 #ifndef BORNAGAIN_GUI_VIEW_DEVICE_DISTRIBUTIONSELECTOR_H
 #define BORNAGAIN_GUI_VIEW_DEVICE_DISTRIBUTIONSELECTOR_H
 
-#include "GUI/Model/Project/ID.h"
 #include <QComboBox>
 #include <QFormLayout>
 #include <QWidget>
@@ -37,6 +36,9 @@ struct MeanConfig {
 class DistributionSelector : public QWidget {
     Q_OBJECT
 public:
+    //! Which distributions should be available in the selector
+    enum class DistributionsCategory { All, Symmetric };
+
     /// \param mean_config controls how the mean value is shown and can be input.
     ///                    If this parameter is \c nullopt then the mean value can not be input
     ///                    and only symmetric distributions are provided
@@ -44,11 +46,11 @@ public:
     ///      (i.e. the combination of all distributions without mean input is currently not
     ///       supported)
     DistributionSelector(std::optional<MeanConfig> mean_config,
-                         GUI::DistributionsCategory distributions, QWidget* parent,
+                         DistributionsCategory distributions, QWidget* parent,
                          BeamDistributionItem* item, bool allow_distr);
 
     BeamDistributionItem* item() const { return m_item; }
-    GUI::DistributionsCategory distributions() const { return m_distributions; }
+    DistributionsCategory distributions() const { return m_distributions; }
     void refresh();
 
 signals:
@@ -62,7 +64,7 @@ private:
 
     BeamDistributionItem* m_item;
     std::optional<MeanConfig> m_mean_config;
-    GUI::DistributionsCategory m_distributions;
+    DistributionsCategory m_distributions;
     QFormLayout* m_form_layout;
     QComboBox* m_distribution_combo;
 };
diff --git a/GUI/View/Device/GISASBeamEditor.cpp b/GUI/View/Device/GISASBeamEditor.cpp
index 97df4aa6aebfe1baff0e255b47228a67540034af..0babafaf03150eefe3bf1a4aab3f9deefef96053 100644
--- a/GUI/View/Device/GISASBeamEditor.cpp
+++ b/GUI/View/Device/GISASBeamEditor.cpp
@@ -40,20 +40,20 @@ GISASBeamEditor::GISASBeamEditor(QWidget* parent, BeamItem* item)
 
     // Main row: fixed values or distributions for wavelength and angles of incidence
     auto* wavelengthEditor =
-        new DistributionEditor("Wavelength (nm)", MeanConfig{true}, GUI::DistributionsCategory::All,
+        new DistributionEditor("Wavelength (nm)", MeanConfig{true}, DistributionSelector::DistributionsCategory::All,
                                this, item->wavelengthItem());
     connect(wavelengthEditor, &DistributionEditor::distributionChanged, this,
             &GISASBeamEditor::dataChanged);
 
     auto* inclinationEditor =
         new DistributionEditor("Grazing angle (deg)", MeanConfig{false},
-                               GUI::DistributionsCategory::All, this, item->beamDistributionItem());
+                               DistributionSelector::DistributionsCategory::All, this, item->beamDistributionItem());
     connect(inclinationEditor, &DistributionEditor::distributionChanged, this,
             &GISASBeamEditor::dataChanged);
 
     auto* azimuthalEditor =
         new DistributionEditor("Azimuthal angle (deg)", MeanConfig{false},
-                               GUI::DistributionsCategory::All, this, item->azimuthalAngleItem());
+                               DistributionSelector::DistributionsCategory::All, this, item->azimuthalAngleItem());
     connect(azimuthalEditor, &DistributionEditor::distributionChanged, this,
             &GISASBeamEditor::dataChanged);
 
diff --git a/GUI/View/Device/ScanEditor.cpp b/GUI/View/Device/ScanEditor.cpp
index bc44f084888c33556328b673b73dc3d8b1664fe6..0f47bad3332ca190b74668c7cfd50d3324e6abba 100644
--- a/GUI/View/Device/ScanEditor.cpp
+++ b/GUI/View/Device/ScanEditor.cpp
@@ -50,7 +50,7 @@ ScanEditor::ScanEditor(QWidget* parent, InstrumentItem* instr_item, ScanItem* it
     layout->addLayout(hLayout);
 
     auto* wavelengthEditor = new DistributionEditor("Wavelength (nm)", MeanConfig{true},
-                                                    GUI::DistributionsCategory::Symmetric, this,
+                                                    DistributionSelector::DistributionsCategory::Symmetric, this,
                                                     item->wavelengthItem(), allow_distr);
     hLayout->addWidget(wavelengthEditor);
 
diff --git a/GUI/View/Main/CentralWidget.h b/GUI/View/Main/CentralWidget.h
index 773900dbef273a471d210d2db66a189fd5b3923b..23f0fca075f5b55cfcdc16a9597068e00403791e 100644
--- a/GUI/View/Main/CentralWidget.h
+++ b/GUI/View/Main/CentralWidget.h
@@ -15,7 +15,6 @@
 #ifndef BORNAGAIN_GUI_VIEW_MAIN_CENTRALWIDGET_H
 #define BORNAGAIN_GUI_VIEW_MAIN_CENTRALWIDGET_H
 
-#include "GUI/Model/Project/ID.h"
 #include <QButtonGroup>
 #include <QProgressBar>
 #include <QStackedLayout>