I was just taking 300secs darks and realized the set temperature threshold was not taken into account during the session, but only at the beginning? Is that the intended behavior?

When a job starts, it sets the temperature and wait when it is in range. It does not actively check temperature between images though.

Would it be possible to implement that the same way like the constraints for guiding and focussing, so it gets checked during the capturing process as well?

It happens to me, that e.g. I set the temperature to 0°C and tolerance at 0,5° that when I start capturing, it starts when it reaches 0,5°, but the cooling is so laggy that it actually goes further down until -13°C and only then comes up again to 0°C. So assuming I need to have calibration frames at the same temperature, I can use the first lights.

It would be nice to wait until the camera has found the right cooling level and does not oscillate around the target temperature anymore. Even if the "waiting" is implementing by starting capturing and aborting when the tolerance bands are left. Same as with the guiding and focussing.