I've been playing the game since the early 2010's, about 1500 hours logged.
I think I tried using the docking mode once... that's it. I didn't see the point of docking mode. It just moves your RCS controls into a new, less versatile layout.
I had expected the docking mode to give me some kind of angle of approach indication, but all it does is shows momentary velocity change as you make it which is kinda useless as you already know you changed velocity, you're the one who fired the thruster, lol. It has no practical use, you're still having to line up your docking ports by eye anyways, so why bother entering yet another control mode to do it?
I've checked back occasionally after various updates hoping they've actually made the docking mode useful (by adding actual alignment angles to target) , but they never did.