Signing a.k.a. sign language can be helpful for people who are hard of hearing, as well as for video calls, loud rooms, etc. Some teams like use signing in all meetings because signing is fast, easy, clear, and keeps things on track.
Voting: thumb up means yes, down means no, sideways means maybe. Everyone votes and the leader tallies.
Clarification: make the letter "C" hand sign. Everyone pauses and the leader figures out what's needed.
Ask to speak in turn: raise your open hand. Everyone will let the person speak when it's their turn.
I understand: make the "OK" sign.
I don't understand: raise your open hand to your chest, palm facing front, and move it side to side.
Please be louder: raise your open hand to your ear, palm facing front, so the moderator and/or speaker notices. This can indicate "please turn on your microphone".
Please be quieter: make the "shhh" sign with your pointer finger at your lips. This can indicate "please turn off your microphone".
Please stop/freeze/wait: hold up your closed fist, fingers facing front.
I'm typing in chat: show your hand and move your fingers as if you're typing on a keyboard.
Time check: point at your wrist. This means please be aware that there's a time limit coming up.
Time out: make a "T" sign with one hand on top of the other. This means conversation stops and the facilitator starts.