Reprap firmware issue

I I’m using laser web with reprap firmrware and i have a problem with laser cuting.

Reprap firmware need a S power in each Line on the gcode note only at the begining

Something like that :
G1 x15 S255
G1 x25 x10 S255

How can I do this or is that possible to implement this functionality ?

Thanks !

This is the default behaviour of the “Generic GRBL machine” profile with the default gcode generator. Have you tried to apply that profile?