CCT says the slot ID for the referee is 255. Another NPC ref, idk, for cutscenes maybe? is in slot ID 571. It's been a while since I installed refs in my game, so I'm not sure what those correlate to. I have Hebner, 2 versions of Charles Robinson, and I believe an ECW ref all installed. Also got Aubrey Edwards on my AEW mod. The majority of those were installed via drag/drop. They're all named different and replace certain refs, I assign them to shows to keep track of them. Haven't figured out renders for them myself.
Hope I've been of some help. As I said in my post to B4G, I'm just using a handful of tools and trying not to brick the game. lol
Edit - looking through my game, Earl Hebner replaces Old School Ref 1.
WCW Nitro 1999 Charles Robinson replaces Standard Ref 2.
Classic WCW Charles Robinson replaces Standard Ref 3