If you use the variables [extruder0_temperature] or [bed0_temperature] in your starting script, then you can control where the heatup commands are placed (i.e. the software won't add them automatically at the top of the file). So it might look something like this:
Code: Select all
G28
G29
M140 S[bed0_temperature] ; start heating bed
M104 S[extruder0_temperature] T0 ; start heating extruder
M109 S[extruder0_temperature] T0 ; wait for extruder to reach temp
M190 S[bed0_temperature] ; wait for bed to reach temp
Note that you replace 0 in extruder0_temperature with the correct temperature controller identifier for your extruder (i.e. T0, T1 etc), but usually it's 0, so maybe you can just use it as is
There's more info about this type of stuff here:
viewtopic.php?f=8&t=1959