Following the same pattern as what we ended up doing for macOS (Change macos/osx tag synonym), I think the best approach should result in picom as the main tag and compton as a synonym. As I understand it, these would be the steps involved (without moderator intervention):
add a picom to existing compton questions;
make sure any relevant information from ...
I suggest this procedure:
If the tag is used on sufficiently few1 questions, then
If you are sufficiently sure1
that the tag doesn’t belong on our site,
simply edit all the questions where it is used, and remove it.
(If possible, replace it with a more appropriate tag.)
This will cause the tag to be deleted if it is not used again
within six to eight ...