Customise end gcode

hi there
i wanted to modify the end g-code to activate the rear fan and put bed up for cooling
i modified in the directory snapmaker-luban/config/printing/snapmaker_j1 the machine.def.json with the move i want at the end g-code section:
“default_value”: “;— End G-code Begin —\nM104 S0\nG92 E0\nG1 E-1 F300 ;retract the filament\n\nG92 E0\nG28 X0 Y0:home extruders\nM140 S0:put bed off\nG28 Z:home bed\nG0 z200:move bed upper\nM106 P1 S255:start rear fan\nM190 R40:wait until bed goes to 40\nM140 S0:bed off\\nM107 P1:fan off\nNG28 Z:home z\nM84:stop motors\n;— End G-code End —\n”

but it never inserted, i always got :;— End G-code Begin —
M104 S0
M140 S0
G92 E0
G1 E-1 F300 ;retract the filament
G92 E0
G28 Z
G28 X0 Y0
M84
;— End G-code End —

i tried to modify in snapmaker-luban/config/printing/ the active_final.def.json who is having end g-code, i modified it and saved it, created a gcode and notepad++ tell me that is was updated, so i look at it and it was like before

someone can point me at something
thanks