When reviewing a suggested edit, you can give a custom rejection reason, and when you open the rejection popup and someone already voted to reject with a custom reason, you get a blue (1) indicator after the "custom" label next to the text box.
I propose that, when someone votes to reject with a custom reason, there's a "new" rejection reason added to the list, which is that custom reason. A bit similar like what happens with custom close vote reasons. I think this would be a good idea because it could accelerate the rejection of bad edits that wouldn't match one of the existing reasons, because then just one person has to type the rejection reason, other people can just reuse it.
Visualization of what I mean:
