Found the answer at Use Reactions, Presenter Overlay, and other effects when videoconferencing on Mac - Apple Support
Scroll to Manual framing adjustments and you'll see the below (copied for your convenience)
Requires macOS Sonoma or later on a Mac using an Apple Studio Display, or macOS Sonoma or later on a Mac using Continuity Camera with iPhone XR or later
- From the Video menu
- in the menu bar, make sure that Center Stage is turned off (dimmed).
- Center Stage automatically makes framing adjustments, so it must be
- turned off to enable manual adjustments.
- Move your pointer over the video preview in the Video menu, then make these adjustments:
- Zoom:
- The zoom control is a series of tick marks showing the zoom level, from
- 3x zoomed in to 0.5x zoomed out. Drag the control left or right to
- adjust zoom.
- Pan: Drag your image within the preview window to pan and adjust the frame.
- Recenter:
- Click the Recenter button to position your face in the center of the
- frame. (To remain centered as you change position, use Center Stage