Just insane how many options there are to customize the livery of just a single wagon!
What I found particularly useful was the 3D view of the wagon. I'm not sure if that is possible with formspecs, but if it is maybe the mouse cursor could change when hovering over the 3D view to indicate one can actually drag/rotate the wagon view.
The only other little thing where I was/am a little confused is the difference between the Livery Template in the Editor's tab and the Predefined Liveries tab. What I believe it to be is that a Predefined Livery is a customized version of an existing Livery Template. I'm not sure about it though.
All in all this is probably the best way to make trains extremely customizable in a simple and player friendly way. Additionally it enables modders and train creators to include multiple predefined liveries for their trains from which players can choose from in-game.
Personally I 100% recommend it!
Thank you, Xenon! I very much appreciate your review and the feedback.
With respect to changing the cursor in the 3D view of the wagon, that certainly would be a good improvement. Unfortunately, I did not find a way to accomplish that given the limitations of formspecs. In the meantime, I will continue to look for other ways to make it obvious that the viewing angle of the 3D model can be manipulated interactively in both the normal and expanded view. I had previously experimented with setting the tool tip, which worked, but it seemed a bit clunky and sometimes obscured part of the model while dragging so I removed it. Perhaps I'll revisit that approach to see if I can find some reasonably short text or set of symbols for the tool tip that would be sufficient.
Your interpretation of predefined liveries versus livery templates is exactly correct. Using the edit button on the predefined liveries tab allows you to view the livery template name and the associated values that were used to create the selected predefined livery. This allows you to not only see how the predefined livery is defined but you can then also use it as a starting point for creating a different livery.