@[supprimé]
That works but the curves unfortunately don't flip. Attachment keys also end up illogical in that situation.
I guess Hwadock is all linear in the example above though. In that case, this sometimes works. SOMETIMES:

The flip shortcut definitely takes the guesswork out of selecting a box of the correct width and resizing it the correct distance, then moving it back. Still. There's more work to do for it to work nicely because of the problems I mentioned.