Hi Michael,

> are you asking for something different with this extend
> mode than what can already be done with "untrim" / delete trim edges ?)

Well, sort of, it does the same thing but without going through the paces of separating, picking and finding all the edges, and you always miss that tiny edge, then deleting.
Where with an enlarge button or even a script for now, it would be; execute command, pick surface, done.

For the second part, extend a surface to a boundary sounds interesting, I don't believe I've seen something like that.

Cheers