Hmm, very weird, that was one thing that could be checked by myself that it appeared in the movers. I just couldn't test with the button actually appearing in dungeons.
Edit: Okay, reverted back to the 5.07.21 version with the nUI_Button and nUI_UnitPower fixes applied and the bar mover appears in the /nui movers screen as this screenshot shows. It did take me a while to find it amongst all those movers though rofl.
Just realised that the nUI_Button fix post wasn't in my signature link ... although it shouldn't have made a difference to it appearing but added it now and heres a link to it anyway.