Lightroom :: Instantly Filter Or Separate PSD From Raw In Catalog?

I have been very reluctant to bring edited PSD master files back into Lightroom, to the point where I regularly purge from the catalog those that accidentally find their way in there.
 
I'm a relative newcomer to Lightroom, having relied on a Bridge/ACR/Photoshop workflow for many years. So partly for historical reasons, raw files and PSDs serve separate and very different purposes in my workflow. Previously, everything went through Photoshop to produce a master file, from which I then batch processed for different output. I still have about a terabyte's worth of old PSDs containing layers, smart objects and whatnot; some of them very complex files. And I still occasionally need to build complex PSDs for special purposes.
 
Anyway, that's the background. What I want is to use keywords and all of the other wonderful Lightroom tools to organize them.
 
But I just have to be able to separate DNG/NEF from PSD at a glance. Or instantly filter one or the other. There's just no way I can spend time looking at individual file extensions in the filmstrip to try to figure out which is which. It has to be obvious and instantaneous, deadlines are always tight, and I'm always in a rush. Color labeling could work, but I already use that for picks vs rejects, so that's not an option. Flagging or rating seems not quite obvious enough.
 
So what's the best way to deal with this? At the moment I have them in separate directories, but this is getting increasingly complicated and confusing. I soon need to clean up and bring everything into a single Lightroom catalog.