Studio is an Intersystems provided tool to edit routines/classes/xml/ etc. used in Caché systems, it isn't a general purpose editor.

If you have a valid Caché system, you could pull up the GT.M routine in a linux editor like pico/nano, copy the entire routine into the clipboard, then paste into a new .MAC routine in Studio for editing, then when done, copy/paste back into nano and save.  A lot of effort that doesn't add any value.

I highly recommend Serenji if you are going to edit/manage M systems on multiple vendor platforms, it is very good.

Mark