GUI data view: replace drop-down list (heat map | projections | mask editor | fit) by action buttons
Functionality offered by this drop-down list is somewhat hidden; personally, when I was looking for the mask editor, it was not occuring to me to search search for it under the "heat map" button. Also, this lists makes features mutually exclusive without any need. There is no reason why "projections" cannot coexist with "mask editor". And a "heat map" is always shown, even if another feature is selected.
Therefore, replace this list with action buttons, just like the extant ones (Center view | Save | Fourier | etc).