I play on a server where very few people have the mod installed, and I'd really appreciate an easy way of disabling it without relaunching the game (such as a keybind, or a toggle switch in modmenu, etc) for when I'm talking to people who don't have the mod installed, or just want to talk to someone in a different location.

This is a valid suggestion. Forge at one point in time was providing a disable button but it was for a long time not properly implemented back then.
I should check if it now works (or was completely dropped by forge). Alternatively either we provide a cli command or see if there is another api which facilitates such feature.

See also #6

seems like 1.18.1 still does not easily support configuring via forge ui