No worries! I renamed the "scenes" via the on screen menu with remote . Glad I could help!!
I was able to rename the Scenes using on screen menu, the web-interface and on the AV Controller app.
On the RX-A3080, the name change reflected on MusicCast app.
However, on the CX-A5100, the name change did NOT reflect on the MusicCast app.
So I conclude that the CX-A5100 (and older AVR like RX-A3070) did NOT get this feature upgrade. The CX-A5200 probably got this upgrade along with the RX-A3080 and all newer AVRs.
But anyway, I am now only using MusicCast app as my Remote. AV Controller app is now retired on my system.
My phone Volume buttons serve as my Master Volume for the Yamaha. Super cool.
My setup is extremely simple. I only have 2 Sources: HTPC and Music Server. And 2 Scenes for HTPC: Scene 1: Straight Mode, Scene 2: NeuralX mode.
My conclusion: MusicCast app is the best WiFi Remote Control in the world.