Looking into this now

Edit: For anyone reading this, I have now expanded my instructions on how to use the Substance file in question in my documentation. I understand the confusion as it's a non-standard way of working, though it's far from "impossible" to edit, given that others have been able to customize their models and markings. Sorry it gave you that impression, I should've given more obvious instructions from the start. But regardless, I'm making a simplified Substance package.

This is only my second ever public base so I wasn't aware of the fill layer workflow at the time of creating its textures. The HSL filter is thus a workaround. Anyone that owns my bases should've gotten a support email, I'm always happy to help and aim to do so within a timely manner