I just wanted to mention some really helpful features as a pianist that you might consider:
Fingerings - If there could be a setting so that the Fingerings for the RH show up on top, instead of underneath the LH. After reading RH as treble and LH as bass for years, it's hard to use the Fingerings when they seem to appear inversely.
Fingering numbers overtop of the notation image - There is a one octave notation of the scales written in the circle of fifths tab. It would be neat if there was an option to display written fingering above - like Hanon, etc.
Arpeggio Fingerings - It would be really cool to have an arpeggio section under the scale section, where a full chord can be seen as a broken chord, and include those Fingerings as well. For instance, the second note in C maj arp is E and in the LH it is played with finger 4. D major arp would be played with 3 on the second note, F#, etc.
Multiple octave view would be helpful for scales.
Ascending and descending view would be amazing.
These are basically all of the functions I would need as a pianist to replace my Hanon/Jazz exercises in my forScore binder. Until then, great work - it's a neat app as is! My last comment would be that if you work with forScore as a third party plugin to generate scale/arpeggio studies, I feel like many forScore musicians would find the app useful.