+1 for this! Some considerations I thought of: 1. smaller keyboards don't easily have access to upper octaves. 2. User might frequently change the transpose on their keyboard.

Could there be a Create Bookmark Now button in the app as a fallback?

The octave is configurable :)

And if you choose, you can make it slightly harder to invoke by requiring an additional 'function' note to be held down.

I haven't felt need for a bookmark button in the app yet, but it did cross my mind.