How can a pair seated at a table or non seated join another table as a pair

In 'DIDO' Tourney rooms, the IMPS Tourney, the Improvers Tourney one cannot join another table as a pair (or a single player) The server will randomly combine the seated pairs. 
In rooms like the Social Room, the Daily-non DIDO- room, the coaching corner one can join an incomplete table as a pair or as a single player.
If you are already seated but want to join a different table, press [Leave Table] and then sit at the desired table.

The Rooms Timetable has links to explanatory web pages of the various rooms