See my Guide:
Bottom-line up front: For the External Camera, you can’t do it interactively. You’d have to hard-code it then Fly.
It means you’re very limited in what you can do by manipulating the Cameras.cfg file in the sim. You can change the Initial Zoom value on any External Views Definitions (which I haven’t been able to translate what it means to from an actual Zoom slider view), but the bottom line is that since you cannot EASILY modify your relative position AWAY from the plane, it’s not a big return on investment so to speak. In Cameras.cfg, there is a InitialXYZ field for the camera. You would need to edit this for each aircraft file, then experiment depending upon size of the plane etc. You’d have to edit the file, load the sim, load flight. Experiment, and repeat. Very unwieldy. And would it get overwritten each time by the Updates? Unknown, but most likely.
The Answer is to use the Drone View. For that, I keep an XBox Controller nearby and use Set Pause ON/OFF to freeze the Decisive Moment.