Activating the star icon on track in NLA Editor causes all exported animations to be duplicates of action in that track · Issue #964 · KhronosGroup/glTF-Blender-IO · GitHub
Tracks — Blender Manual
animation - How can I combine 3 actions with the NLA Editor? - Blender Stack Exchange
animation - Bake/Merge two or more NLA tracks into an action - Blender Stack Exchange