Atlas is indeed ambitious, and I am glad you want to push the boundaries.
Over the decades, GUIs have introduced a bewildering array of widgets and designs that I think we are in a mess again.
I feel we should restart again with a blank window, allow select and rightclick for context menu, and proceed for there to introduce the base minimum for a functional GUI.
I believe "select and rightclick context menu" can solve almost every GUI need simply.
I also think the single column menu can be updated to a two-column menu which is more compact and balanced.
The cursor can be centered between the two columns instead of being at the top left corner.
The cursor has to travel less for any selection.
https://askoh.com/index.html#TwoColumnMenu