You will only see it in the prop it up mod ui when attempting to replace a decal like parking or tiles. The mod must be in extreme mode also. I dont replace decals or use extreme mode anymore as I had an epic fail of sorts and I had to delete the file containing the mods info on all the buildings I had changed and resub. Which may or may not have been the fault of the mod itself but just to be safe now I delete decals in the editor. Which doest take that long if you do several at once. I believe it's called 'prop it decal'.
I hope this answers your question. XD

What is the decal called so I can find it in game?