Forgot another feature from an editor a friend and I developed and used for many years...
Multiple block/box selections that are stacked in a first in, last out queue. You can operate against these selections across any file buffer. The use case is usually something along the lines of:
Edit files A, B, C, D.
Select some method in A, some lines in B, some box in C. Edit D and then start copying or moving those blocks into D. For example, the first copy would work against the box selection in C, then deselect it. The next copy would operate on the lines in B, finally a move would move the method from A to D (leaving both files modified).
Maybe something similar to this exists in SE today, but I'm not familiar with it.