On this page of the documentation for the profiler (under the header "GPU-bound app"), it refers to a "GPU % Utilization" indicator.
This is exactly the information I've been hoping to obtain!
But sadly, upon connecting a device and launching an app, I can find no such indicator. I've tested with a few different Adreno GPU mobile phones (eg 540, 630)
Here is a screenshot from my program running, searching all indicators including the word "GPU". (I've also searched through everything manually): https://imgur.com/ejATn4m