If I’m in a room with people I know and I plan to leave the room for a long time, I tell them where I’m going. If it’s for a short time I do not.
What (if anything) is an appropriate time scale to leave a room without announcing when/if you’ll be back?
I’d say anything longer than five minutes, with anything less getting at most a “I’ll be right back” with a gesture in the direction you’re going.