knockout transparent color

I know I have asked this before, but I don't know where the original post went. I would like a color that, when placed on an object over the top of any other object in that layer, will make all other items or objects below it transparent, creating a knockout effect. It’s essentially a knockout group or knockout color, but it's actually just a color swatch that forcibly knocks out and makes transparent any object or item underneath it in a layer.

The reason I’m asking is that when I flatten and expand appearances, it removes my knockout, and then it's forgotten because it either matches a similar color or gets skipped entirely due to being an invisible layer. It just removes it during the expand process.

Either we need to fix the expand so that it recognizes a knockout and properly removes it from the items, or we need to have it as a custom color so that when I expand, the color is revealed, allowing me to knock out the elements before I finish expanding. I’m trying to do this process for screen printing.

Normally, I use the background color as my knockout color so that it’s more clear. However, I would like to be able to change my background or have dynamic backgrounds with textures rather than just a solid color.