Here's a gif of an example of this use-case.
The icons are all .png files, not shape layers. As you can see, the shelf icons overlap. Due to the transparency of the .png you can see other shelf icons through the books on the shelf. With the old method of using track mattes, the way I would have dealt with this was:
- Make an adjustment layer
- Add a mask to it tracing the books that I want to "cut out" of the other two shelf icons
- Move the adjustment layer above the second shelf icon
- Parent the adjustment layer to the f

