Screenwriting : Paranthetical shortcut? by Tony McFadden

Or stick it in action line. Steve can hear someone outside, fearfully he whispers.

Add a physical attribute like a twitch or jerk, smirk or raise of eyebrows. Maybe even the rolling of eyes?

I'd just add it before they start conversing in your scene heading, ie; "The two put their heads together, whispering."

If you know they are supposed to be whispering won't the actors and the director be able to figure that out from what is happening in the scene. If so then you don't need any actor's directions.

Action lines.

Steve scoffs and looks off for a moment.

Bob nods slowly and rubs his chin.

The president stops paying attention and tweets on his phone. Etc...

In the action as others have said or a note. I prefer as a simple action "Bob and John put their heads close together and begin whispering" then dialogue. Same for if the whispering ends in the same scene and transitions "Bob nods at John in agreement. They turn and address the other lawyers at the table."

May not be right but it's clear at least if not bordering on directing however.

Show it in your scene - you don't need to tell me or your actors. Film's a visual art form - SHOW ME.

I agree with Doug.