The only way I know of how to make seams are along edges and vertices. But is there a way to create "custom" seams between faces without adding geometry to create ID color maps for texturing purposes? Hopefully the question makes sense. For example, left is the default geometry, right is where I would like to add a seam for a utility belt.
I'm aware I could probably just add an edge loop there without much consequence, but there are other examples where that isn't an optimal solution so I'm exploring my options here.