I don't use the trackside camera much (I like the principle but not the implementation) so I decided to sacrifice it for a modified version of the external follow camera (key 2). This is what I did:
1) backed up TrackSideCamera001.bin (and the corresponding xml) in Assets\Kuju\Railsimulatorcore\cameras
2) copied and renamed ExternalCamera001.bin (& xml) as TrackSideCamera.bin (& xml).
3) used RW-Tools to edit the entry in the resulting TrackSideCamera.bin that reads <FollowTargetMovement d:type="cDeltaString">eTrue</FollowTargetMovement>, replacing 'eTrue' with 'eFalse'.
That's all. Very empirical and done with little understanding on my part, but the result is just what I want. When I'm using the external front camera in a position ahead and to the side of the train (zoomed out a little way) I can pick my moment then press key 4. The camera stops moving but pans around as the train goes past. All very seamless. Then I might jump ahead of the train again for a while with key 2 and repeat the process. Very satisfying - and to my mind it's a more natural way of watching trains in the landscape than the helicopter view of the follow cam. Just the ticket for the feast of highly scenic routes which we're enjoying at the moment.
Alternatively the detached camera (8) can be positioned anywhere you wish, then selecting the panning camera maintains the current position but starts panning on the train. A little more fiddly to set up and it jumps initially as it centres the train in the view but you can set up very precise panning views this way. I discovered that the sim can be paused after the detached camera is engaged, allowing the camera position to be fine-tuned without a runaway train bearing down on me
You probably knew that....As I said, this is not original or sophisticated so don't scoff at my efforts. I'm hoping someone with more understanding than myself might enlighten us as to further possibilities. For example, can a new camera be created so that an existing one is not lost? And what is the 'cinematic camera' in the same folder? It's probably exactly what I wanted but in my ignorance I couldn't get it to do anything.
Have fun.