You may not be able to do it at the control if there are no () keys..sucks I now..My OTc also does not have a "full" key pad..
You may have to do like I did in the days of programing at the control ...after the program is built, post it to a editor and add the comments..
I now program everything in my cad/cam software. It automatically adds the comments where I want.
Maybe someone else knows if a OiM will take something other than ( ) for comments..my bet is not..been wrong before though.