Hold button is not available for multiple participation meetings.
Hold button is available for 1:1 calls on MS Teams but,not available for multiple participation meetings.
Kitty Cee commented
Microsoft: PLEASE make this option available. It would really help students stay in their main class meeting when switching to other classes that require sound (other video conferencing apps, online activities, etc) without having to leave Teams meeting and rejoin after to avoid hearing what may go on with other students that stay in Teams.