When trying left and right mouse scrolling in piano roll there is a bug which causes scrolling goes up and down. Left and right scrolling works Write section but not in the piano roll. Shift + scrolling works in the piano roll but left and right scrolling would be handy because many mouses support it. That’s my feature request in Dorico SE and Pro versions.
Welcome to the forum, @Timppa90. I’m sorry, can you provide a bit more clarification as to what you’re asking for? Is the issue that you have a mouse with a tilting wheel that you can push to the left and right, or that Shift+wheel doesn’t scroll horizontally in the Key Editor?
Mouses for example Logitech G903 or G502 lightspeed has feature to horizontal scroll left or right. I guess it is that tilting wheel thing. Just hoping that feature is in the piano roll for mouse in Play and Write mode in Key editor. Shift + scroll works fine and that way new horizontal mouse scrolling should work too.