You can use this "Camera" effect (free download):
https://fcpxtemplates.com/downloads/
It's an effect. There's a couple of different ways to use this.
1) Just add it to any clip. Make sure the effect is at the bottom of the Effect list (or deal with some unusual interactions -- no big deal). When you're done with it -- or just want to go back to "normal" -- simply "uncheck" the effect in the inspector.
2) Add it to any adjustment layer title (can be stretched out in time to cover many clips at once.) Select the Adjustment Layer and type the V key to toggle it's "visibility".
There is an OSC that will help you pan around the image while scaled. (Best to set the Viewer to Fit or 100% — not scaled up to begin with).
Scale is *not technically* used - Z position is (distance of camera to the "scene"). The high value goes to 2000 which is approximately 360%-400% "zoom" (I think...)
I have found that the image quality in the 300% or so scale equivalent is better than a similar effect that uses a straight "scale".
I never finished developing this effect, so it's not terribly practical for anything else, but it will serve you in a smooth scale from 100% to ~400% with excellent results with onscreen panning for looking around that may suit your purposes.
If you need help installing it:
https://fcpxtemplates.com/installing-plugins-for-fcpx/
If you have any questions... just let me know.