Use a separate timer for the cabin heating if required although you should be able to combine without difficulty.
Do you ever see the car actually use the EVSE to preheat? I have not done any exhaustive testing, but watched my car while connected to an EVSE to start preheating. Even a couple of minutes into it, the EVSE was not being used (it was briefly enabled by the car when it woke for maybe 2 seconds). With a Tesla (drove those for a decade), the shore power is always used to save cycling of the battery, it is clearly noticeable if you watch the car after engaging preheat. Heck, Tesla uses shore power first always when plugged in (e.g. if the car is plugged in and you enter and turn it on, all the power for HVAC and and even the 12V is powered from the EVSE, if it can provide up to 3-4KW), not so in a Taycan. I never had enough patience to sit in a fully charged Taycan with it on byt plugged into the EVSE, and watch the battery SoC drop to see when it would actually engage the EVSE and at what charge rate. Will it just let it drop by few percent then charge at full rate (19.2KW in my case) back to target SoC, so essentially continue to cycle/discharge-charge the battery while in use and plugged in?
You can create a timer (departure timer) which only has the air conditioning / heating set and is independent of any other timers.
Mine heats in 5 - 10 mins. Sounds like there is a setting conflict rather than a fault.
Yeah, this is what I have been using (with charging deselected). When I used it with a correct departure time set it used 5% of my battery to warm the car, which seemed excessive.
Do you mean 5-10 mins from when you manually trigger it? If so, I agree, mine does too. It just seesm that when triggered from the timer it starts warming up way earlier than 10 mins.
I generally do 'it manually prior to departure (if I remember).
See my post above. I think the time is dependent on the temperature and at the moment takes about 20 minutes if you set a departure timer
