I've been looking around for this feature, and pardon me if I missed it.
Recently I've started using a lot of window management hotkeys, and I've started to get really annoyed by the fact that once I do an action to a window, I'll have to manually revert those changes if I want them undone. Therefore I thought about making the changes revertable.
For this I've come up with two possible solutions:
1. Make a hotkey that'll function like ctrl+z, but only for actions made through DF. It only has to cache a few action, like 2-3, or even just 1.
Example:You do a combination that'll center the window, and give it 20% width and height, then you press the "undo" hotkey, and you'll revert the window's state to whatever if was when you started.
2. Treat every action like an on/off switch.
Example:You do a combination that'll resize the window to 75% width/height from whatever state is was in (let's say 50% w/h). If you push that combination again, you'll revert the changes, and once again, the window will be 50% w/h). This of course should only apply to actions that involves resizing or fixed positioning (means it'll work for "move to upper right corner", but NOT for "move to next monitor").
This is an interesting idea, and not trivial to implement. I think your first suggestion is the easiest (and least complicated) way of handling this. I will add this to my list of HotKeys to investigate for a future release, but I can't make any promises about timing. Thanks!