Ah... Well, scrolling is not necessary, you could make the user jump to several "boards", each board being a part of the big sequencer.

So like patterns and playlist in FL? Woohoo.... somethin' big coming up

I wasn't thinking at patterns and playlists, but just at a way of avoiding scrolling.
This would have became TIStudio. ^^

But thinking of the idea of patterns and playlists, I guess it could be doable...

Maybe the num keys to switch between the patterns (1-8) and another screen for the playlist. If you press play in the pattern screen, it only plays the pattern, if you press it in the playlist screen it plays the whole song, looping through each pattern. Graph will display the playlist, the Keys 1 - 8 the patterns.

With the select function you will only be able to highlight complete bars, but you can copy, cut & paste them in and to all patterns.

Buttons + and - will increase or decrease the speed, the arrow keys are for vertical and horizontal shifting of the selected part.

The STO-> will save the whole song, LN will load it.

Lot to do, but the work will be worth it, I hope.