I need to use leveling layers to adjust the gradients of my layer mask. However, Photoshop doesn't support that. I tried using a clipping mask, but a clipping mask uses the alpha channel, not the brightness of the pixels to mask. So this doesn't help me either, because leveling layers cannot be applied to the alpha channel. How do I do this?
Edit: A quick example
In the upper half I have an image (here the Dragon Ball logo) and a layer mask (here just a simple gradient).
However, in my actual use case, I need the result to blend into the rest of the image perfectly. That means I need to fine tune the layer mask.
So in the lower half, I created a group with the gradient and a leveling layer to tune it. Now, I could collapse the group to a single layer and use it as a mask for the (logo). But then I would lose the ability to fine-tune. The environment it needs to blend in might change and I will be unable to readjust. I also don't really get a preview of how my (logo) will look like with these settings.