Nate ha scrittoIt's not clear why you'd need a dummy bone/slot for those actions?
Okay, for example, I have a foot sprite with 10 "FootWalk" frames. Today I added 24 new "FootRun" frames. The first frame of each is identical. Shown here, the foot slot is at position -56, 17.

If I were a new user, I would probably think "time to drag the new frames on top of the foot in the viewport". But if you do this, you end up with 24 separate slots showing up in a kind of grid. So that's not going to help .

The next thing you might try is to drag the frames on top of the foot slot in the hierarchy view. If I do this, the new frames all come in together, but are located at -63, 21. This is because they are centering themselves on the parent bone, rather than on the current position of the slot. So I would need to adjust all 24 new frames to be -56, 17.

So your next thought might be to get them positioned correctly globally, then parent them later. So if I try to drag the first frame of "FootRun" over to where the current foot is, it creates a new slot at -55.379, 17.41 (which is as close as I can get it). So I type in -56, 17 because I want it to sync up with everything else whenever possible.

But that only takes care of the first frame. So I drag over the other frames in the hierarchy view. But these all appear at 0,0 (off the edge of my screenshot). So to reposition them all, I would need to manually enter -56, 17 to get them in the correct spot.

The last resort is to then make a dummy bone. I always leave one in my projects at 0,0. I name it "zdummy" so that it sorts to the bottom of the hierarchy, making it less of a distance to drag the frames in. I use the method where I first drag in one frame, rather than all 24, since I know doing the latter will create 24 slots.

Then I move zdummy to -56, 17, so it matches exactly the existing "FootWalk" frames. Only now can I drag all the frames over to the existing foot slot to get them matching up.