Hi medium-share,

Apply all materials in the Source project file, then sort it in the XRef manager in the Host Project.

An alternative would be to add a User Data (integer) to the Object and read this in the attached RS Material via User Data (Integer) node out, and use it as a switch inside the Materials.

The User Data stays active while used in XRef in 2026, just explored it.
Example, open this via XRef, User Data is on the object.
CV4_2026_drs_26_TXxf_01.c4d
Screenshot 2026-02-11 at 1.23.30 PM.jpg
Render.

Perhaps having no materials in the Source file might not work for your process, and similarly, the idea to just adding a Material on the right side, which has limitations.

You could also make an input via "Share Your Idea".
https://www.maxon.net/en/

Cheers