I'm a long-time FSX/P3D user new to X-Plane (I purchased it from the Steam store). I've figure out Shift-9 to go into the 3D cockpit, hold right mouse button to pan, double-click right mouse button to lock panning.

 

Is there any way to assign a keystroke to toggle panning mode? I figured out how to assign functions to keys but don't see anything under "view" that looks like it has anything to do with panning in the 3D cockpit. Is right-click/double right-click the only option?

You can assign your hat switches on your joystick if you have them. I use them to pan around and zoom in and out.

I'm not a sufficiently experienced and hardcore X-Plane user to know how/if this can be done with the default X-Plane camera system, but it might be possible with X-Camera - it seems to have a lot of key assignments and that could well be one of them.