values to GCode generator, one per active extruder:
bed_temperature
bridge_fan_speed
cooling
disable_fan_first_layers
fan_always_on
fan_below_layer_time
first_layer_bed_temperature
max_fan_speed
min_fan_speed
min_print_speed
slowdown_below_layer_time
Now it remains to extend Slic3r to correctly apply these values.