It would be great if one could, in all OT features:
1. select and add multiple glyphs and/or classes at once in the "Select Glyph or Class" window:
2. retain the position of the "Select Glyph or Class" window when it's reopened, so that the new window appears where the old one was, rather than display-centered again
3. shift glyphs and/or classes up/down after they've been added
4. select & delete multiple glyphs and/or classes at once
5. have a keyboard shortcut to open the "Select Glyph or Class"
In Class Manager - select multiple classes and duplicate+merge contents into one new class.
In Lookups, when defining refs for e.g. substitution, to retain "Glyph Type" the same way "Kind" & "Filter" are retained from the previous selection.
In any glyph and/or class selection, to have the option of hiding from the list items that have already been added - sth like way that "Select Class Members" works in Class Manager.