Thanks for the reply.
I checked both of my config.g and the .gcode, as well as the additional starting script for the T0 and it was always there, not only in the config.g
I tried to put it into several places, had T-1 in the ending script, beginning of the start script a T-1 followed by a T0, just played around a bit.
When I use this sequence:
M140 S[bed0_temperature] ; get bed heating up
M116 H0 ;wait for bed heater
G10 P0 S[extruder0_temperature] R60 ; set extruder temp
M116 P0 ; and wait for extruder
T0 ; Activate Tool 0
It waits for the bed to heat up, then the tool becomes active, started heating and moving, not waiting until the hotend reached its temperature:
Warning: Tool 0 was not driven because its heater temperatures were not high enough or it has a heater fault
Even if I try the M116 without additional parameter, it does the same when I have the T0 after the heating section.
If I have the T0 before the section, every print which is not the first print after a reset waits forever.
I have multiple printers (not all Duet based), so I prefer to use my old way of working.
If this is a feature I have to deal with it, but maybe it is not ...