what i suggest
during boarding, esp. with low ambient temp, set controllers to OFF so they do the preset 18 & 21°C. if the cold air from the outside gets to the cabin temp sensor the packs have a tendency to go haywire and start cooking up to 60°....
once doors are closed you can set the FWD and AFT cab so about 1 o'clock.
with the increased air flow during TO & climb the duct temp will drop. so just before TO set a warmer temp. and for flights that are only 2/3 booked select higher than normal temp for cruise since there are less human bodies heating up the sardine can.
on taxi in exp. in warm climates use the last minutes before shutdown to cool down the cabin.
you see: an awfully lot of switching for a system that could/should be automatic.