TwinMotion - Should I use Unlink at some point? And if so, how?

Ok, so scenario:

I have most of my geo in my sync’d TM file *I’ve gone through and changed my materials in TM and it looks great.

Now, I realize I had a Rhino layer off when I sync’d it up, and I’d like to update the TM file with that layer that’s now turned on in Rhino. BUT I don’t want the rest of the materials, etc, to get messed up in TM (which they do, if I just click the little Sync “eye” icon in the TM toolbar)

Should I be using “Unlink” in the TM window? And if so, what’s the correct process? I can’t seem to get it right. I just keep messing up my TM file.

BONUS Q: What if I want to add extra geo? Same Q for this.

Thx

Edit: I found a sort of workaround, in exporting the additional geo as fbx and then importing that into TM. But I don’t want to have to do that each and every time I change or add something. I’m assuming I’m just missing some understanding of this plugin.

Alt: Is it possible to turn off “Update Materials” when syncing, so only geo changes in Rhino are updated on TM side?