Bake/Merge two or more NLA tracks into an action

I have two NLA tracks, one is the fist-clenching, and another is the leg-bending.

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I’m able to evaluate them at the same time, so the leg is bent and the fist is clenched.

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But my problem is, how can I “merge” or “bake” these two actions into one? I know merging and baking are different things (to my understanding, merging means simply to put the keyframes into the same action, and baking is to turn all inbetweens into keyframes). I’d like to know both.