I've never understood that either. It seems like the simplest approach - define your refdes and then select it for the Silkscreen and Assembly layers. That works great until you realize the silkscreen text needs to be in a different location than the assembly text.
I define all items on the appropriate layers; if I see something in a decal on 'all layers' I know the decal is not complete yet.
Thanks, so for the most part, you either use Top & Bot Assy layer to do all of this
or use other layer #s then cosistantly to be top or bottom part outlines.
There does nor seem to be any way to then add a pair or associate new two layers
so that they will push & mirror when changing from top to bottom part?
The silkscreen and assy layers are relative to the decal whether it is on the top or the bottom. If you flip a component to the other side it also flips all the silk and assy layers; SM and paste too. I've never tried that with other layers.