What silly thing have I done?

Before when I hit delete in the pattern editor, the cursor would jump to the next line. Now it seems to jump some arbitrary number of lines, and I think around the time it started doing this another line started being highlighted in orange when in edit mode?

Presumably I’ve stumbled on some useful feature, but I can’t figure out what it’s meant to be and how to turn it off - thanks in advance!

edit: Ah I think it was edit step. Should have checked the keyboard shortcuts!

http://tutorials.renoise.com/wiki/Pattern_Editor#Pattern_Editor_Control_Panel look for “edit step”