If I create two actions and I mix them in the NLA, I can bake them but then I get a uniformly keyframed animation, I would like to mix them but without creating new frames, respecting the existingt keyframes, at least in the part where there is no transition.
I like the solution of copy pasting both actions into a third, as far as I know there is no sparse bake in blender and I have yet to find a publicly released script.