When a line is selected within the 'code macro' using the steps bellow:

1. Open Firefox, create a new page.
2. Add Code-macro
3. Type

   actor abc
   actor def
   abc -> def
   

   note: Don't use the mouse, use the keyboard to navigate.

   1. Arrow up
   2. Hold Shift + Ctrl, 2x Arrow Left
   3. Hold Shift but release Ctrl, 1x Arrow Left
   4. Hit Backspace

That action deletes all lines above.