A feature like this will help a lot, especially in this Megascans era.
Hi,
To my knowldege, I don’t believe its possible.
The only fact that a UVs could be scaled up for Texel density and that the decal has his own tells me that it could not be possible.
What you could do as a workaround though, is to add a UV Set on your mesh and connect the decal texture to this UV set. But I did not test it, you are welcome to do so 