You can turn Sybill off (or on) for any single upcoming meeting without changing your overall preferences.
Turn off recording for one meeting
Open the Meetings page from the left navigation.
In the Meeting Recording panel on the right, find the meeting under Today, Tomorrow, or its date.
Flip the Record toggle off. Sybill will not record that meeting.
You can flip it back on anytime before the meeting starts. The per-meeting toggle always overrides your default Recording Preferences.
Good to know
If several participants use Sybill, the meeting is recorded unless every participant's recording is off or someone explicitly turned it off; an explicit opt-out always wins.
To stop Sybill from ever recording certain meetings, add a domain, email, or title keyword to your Block List in Settings > My Meetings.