Do you mean, you have some empty note columns in the left side you want to get rid of?
In Renoise 3.1 you can drag/re-arrange note columns, so this would be one way of getting rid of them. Drag them all the way to the right, then hide them 
Otherwise, tool of interest (updated soon, I guess?):
https://forum.renoise.com/t/new-tool-2-8-3-1-reorder-notes-by-pitch/39315