animation – How to combine and export multiple NLA tracks of 2 armatures (Blender) to Unity?

As per first experience I created multiple tracks (and also “added” more animation to first tracks thinking I edit them but instead I just created more tracks for same animations) for 2 armatures (1 armature hands, 2 armature gun)

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How can I export those to Unity properly? When I export in Unity all I see this:

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In Unity my gun animations does not affect animations of hands (in Blender wrist bones is child of gun root, and gun root is child of hands root) and some animations are not even there…

Can I somehow bake multiple strips of 2 armatures to one animation so that in Unity it will be perceived as 1 animation for the whole object?