Better is a matter of perspective. Someone with 88 keys may find little use for octave shifting (even though MIDI spec goes beyond 88 - so there's still a use - just not as much possibly than ..) while someone with 61 keys may find octave shifting to be the only way to play passages they otherwise do not have the keys for -- regarding expanding the keyboard (without changing the note-to-key relationship) as most useful.

Using shift for anything is going to alienate someone who'd rather have a one-finger control for everything.

More information on the status bar is a good idea.

From Saturday, September 17 2016, 05:59 AM
https://www.yamahasynth.com/forum/button-dont-light-up-when-transpose#reply-12470

I'd prefer there to be a small area on the top/status line of the touchscreen to show transposition. It's about as important as tempo - even more so if you do not have arps/motion control or other tempo-based behavior going on but do have transposition. Something like Eb- for the -9 semi-tone tranposition and Eb+ for the +3 semi-tone transposition. There's also a way to get enharmonics to work - but there's probably not a need to over-complicate. Just a transposed key display on the touchscreen would be much better even if the enharmonic does not match the user's personal preference.

Not stuck on the implementation details.