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?
Always depends on context. If you are out somewhere it is good to let them know so they don’t think you left to go home. If its at somebody elseshouse probably no need to mention, if you are the host then good to let this m know if you had something that will take you away for extended period so they aren’t left wondering. Read the room/situations.