David, "The tfree1.g, tpre1.g and tpost1.g files would be similar, except that tpre1.g would use command M116 P1." is this statement correct in regards to the tpre1 including M116 P1? I thought that M116 P# belongs in the tpost1 file
Speaking of G10, is there a reason it waits until the specified tool is activated to implement active and standby temperature changes since I upgraded to the 1.17 branch?
I suggest something like this in your start gcode:
G10 P0 S[first_layer_temperature] R150
Repeat the G10 command for each tool you are using, and replace the R parameter by whatever standby temperature you want. I think most slicers recognise the first_layer_temperature parameter.