@arma473 Ah, thanks! I was missing step 9 since I was too lazy to open the file in a hex editor.
I don't want anyone to go out of their way to really do anything about this. I think I am a pretty fringe case in my desire to play sandbox on generated maps. Thanks for all the info though as it is pretty interesting to know how the map files, lua files, and .scmap files all work together.
What is needed is a way to add specific seeds to a favorite or 'saved' list. Should allow you to regenerate the map on demand from your personal archive. Add a button for "add latest generated map to your saved maps" and a manual input field for the seed with the same function and you've got a pretty nice feature.
A decal is an albedo or normal texture with an alpha mask to hide the square shape. You could theoretically create decals from any regular texture that you can find on these texture websites, but it is some effort.
Roughness textures are used for PBR workflows and currently the map shaders don't support this. (Though I am working on adding this in the future)
But really you should just google how these textures you mentioned are to be used. You will find much more comprehensive explanations online. Sometimes even directly on the texture websites where you saw them