Can Clara understand a participant is optional?

Yes!

Just tell Clara a participant is optional for a meeting, and Clara will skip checking their availability for the meeting + not mail them but will add them to the calendar invite.

This helps when you don't want your colleague's availability to cause a meeting to be scheduled later and you just want your colleagues to be able to join a meeting if they happen to be available.

This is also helpful if you are coordinating for an attendee and are already providing their window of times verbally to Clara.

Heads up that Clara will not mark the participant as "optional" on the calendar invite.