I wonder if there’s an equivalent node to the Substance Multi switch greyscale, which allows to connect various grey nodes or bitmaps and then generate a menu available in Substance Painter to paint with the shape you choose. Eg windows in the picture enclosed.
You can use the Enum Select Image node. To add another option/input, make a new line in the Case parameter in the Graph Object Editor panel… You can then expose the Enum to add a dropdown menu to your graph’s inputs.
If you have any further questions, feel free to ask!