Is it possible using advanced editing to batch remove a load of off commands from a column in a song?
If so how so?
And if not, why not? 
A brilliant idea to add this to Renoise!!
Well… quite
Really a feature to select a type of command on the pattern editor and ask for changes to anything the same in the pattern, e.g. an ‘off’ command, including the ability to delete all would be great.
But is there any way to do this using current features?
it’s kinda messy but yes you can!
open the xrns with like 7zip or an unzip tool.
extract the song.xml
open song.xml in a decent text editor, that will allow matching case.
do a find & replace.
type OFF in all caps and replace all instances of OFF with nothing.
once you have removed all instances of “OFF”
save the xml and put the song.xml back into the xrns.
it’s really easy if you open the XRNS leave the program open and just drop the updated file back in.
remember to only do this with a test editor that allows matching case. and make sure case matching is selected or you will totally mess up the song.xml
do a test find before, and make sure it’s not touching other instances of “Off” or “off”.