I guess I hadn't explored the Navigator well enough - it does indeed have some handy features I wasn't aware of. As for points 2/3, I was hoping:
A) For a quicker method than having to explicitly define a work plane before changing the view. In particular to create the view down a line I have to generate an infinite plane using that line as the normal (or draw two lines perpendicular to the initial one at some point on it), then set the workplane to the new plane/line pair, then view the plane. It works, it's just more steps than I'd like - and the only thing the extra plane/lines are used for is to define the view, so they're just more clutter on the drawing. (Yes, I can create a separate layer for the user view planes and hide it when not needed, but that just adds another step...) And for some of the things I'm working on I might need to create dozens of view planes (and then remember which saved view corresponds to which ray I'm following) - having a quick "view down the selected line" option would save a lot of work.
B) For an easier way to rotate the view by 90º about the current screen axes - perhaps by Shift-clicking on the Navigator's arrows. Changing the Navigator step size is inconvenient at best - most of the time 5º is fine, changing it to 90º for a single click and then back to 5º again isn't much better than clicking 18 times to get a 90º rotation.
I realize that I can do all of this using the available tools; TCad is pretty powerful, it just could benefit from a touch more friendliness and consistency in the user interface. In my pre-retirement career I spent a lot of time working on user interface development, so maybe I'm overly sensitive to these things; but part of the reason I retired is that my fingers were wearing out from decades of keyboard pounding, so these days anything that eliminates keystrokes and mouse clicks is good!