hhsitemtesting.png
So to me this should create a item data stack thus removing every Your Risky Selfie item. However when I run it only one item is removed as if it's not a stack. What am I doing wrong?
You are not iterating through the stack, popping off each item from stack that is removed.
It is just a matter of relaxed execution that Remove Item from Inventory allows using a stack as input, but apparently it takes just the first item as what to remove. An op that self-iterates if given a stack would likely be plural, "Remove Items from Inventory".
I think this was answered somewhere already, but the issue was that it was using the 'Item' link variant instead of 'Stack' found in the right-click menu.