I also have met with this problem myself, I always thought it would be nice if folders moved dynamically 😃
I'm uploading an example below of the draw order I looked up on the exported JSON file:

I am sure you guys have already thought about this and all is accounted for, but I'm still shooting my shot, maybe there could be a function in the draw order hierarchy tree, to checkmark a folder, so that when we keyframe it, the exported file would have not just "slot" offset, but "folder" offset, so even if we add a new slot to the folder, it would move dynamically in all of the keyframes since the offset is "folder"? and it would be togglable function, not workflow breaking change?
This would make large spine projects so much more manageable, allowing us to animate more than ordering layers in each animation for 200 animations per new attachment.
Also i have a question about the "placeholder" workflow, since we would be moving larger folders with 20+ placeholders lets say, would it be more performance heavy, or would it drastically increase .skel.bytes or .json file sizes?
Thank you in advance for your time to reply.