I think I've read all the NLA/GTLF export posts in here, but none of them seem to talk about the issue I'm having.
I'm creating a pop-up book that will be controlled within a WebAR experience by pressing a "turn page" button. Each time the button is pressed, it runs the animations in the .glb file named "turn_1", "turn_2", "turn_3", etc. Since every page element has to pop up when its page is reached, then animate back down on the next turn, and also have an animation for staying down for all the page turns before and after, it means I have to add an NLA track to every single object for every page turn.
Luckily it's just a 6-page book, but it's still proving to be very complicated and overly tedious. I've found ways of making the process more manageable, but there's something that seems like a bug that's making it more complicated that it seems it should be:
For the animations that are basically just a single keyframe which tells an element to just stay at 0-0-0 rotation, I had thought I'd be able to just make one Action with a 0-0-0 rotation keyframe, and name it "Sit Still" or whatever, then just re-use it for every element before and after its pop-up and pop-down animation. Because I'm always pushing it down into an NLA and naming it accordingly as mentioned before ("turn_1", "turn_2", etc).
But the issue I'm running into is after the first use of it on an object, then next one is either ignoring it, or flipping it 180-degrees, it's difficult to figure out exactly what's happening... but it's no staying at 0-0-0. The only workaround I've found is to duplicate the action 6 times and name it with "STILL-A", "STILL-B", "STILL-C" at the end of the Action's name etc, and for each object never use the same exact action more than once.
That works fine for basic elements that are only being animated to rotate on a single axis, but I have a lot of rigged objects that have to have custom armature animations. This means if I were to use this workaround, I'd have to create 6 different copies of the same "Sit Still" armature animations for every rigged object. The number of actions is getting out of control, and is turning into a huge headache.