You can zoom in/out using the View angle slider. You can move along the trajectory using the Frame slider.
If you want to slightly deviate from the trajectory - “look around” - you can:
- rotate the camera in the 3D view by left-click-and-drag as usual
- set up a mouse gesture for moving the camera focal forward/backward - just copy-paste the code snippet in this post to the Python console and you can move forward/backward using Ctrl+MouseWheel. This custom gesture is needed because the usual MouseWheel gesture just moves the camera towards or away from the camera’s focal point, which is not what you want in endoscopy when you are so close to the focal point (because you cannot ever go beyond the focal point).