For the Unload command (similar to the M600), you can set that in your PrusaSlicer's Tool Change gcode, the command for that would be: M702 (I guess you would want this prior to M600).
Another option is to insert the M702 in your M600 macro (filament-change.g in /sys). This will automatically do the Unload for you.
Regarding the the automatic cooldown, I have not seen any way to do this yet. For me, I am typically close to the printer while printing, and especially if there is a need to change filament, I am on standby for it (so the filament don't cook in the nozzle).