How to re-teach pooing outside?

[roseopose]

Argh I've broken my cat/s! We have two, one has always gone out but was shut in at night after losing her sister on the road -she always shits in my flowerbed/wees outside and presumably uses the tray at night if she needs. 2nd goes out supervised and never out of the garden, uses litter tray for everything, will pop back in to 'use the toilet', eyeroll. We moved house at the end of January and kept both in for 4 weeks. They're now both out but shut in at night still. New area much more rural and safer. The thing is now both of them are coming back in to use the tray! I was really hoping to teach cat 2 to go outdoors and didn't expect cat 1 to just forget. I know obviously I need the tray for overnight but really would rather they only used it then, it's also costing quite a lot changing it much more frequently with both using it all the time. Any tips please?

Don't know if this will help, but my friend had a similar situation.
She gradually moved the litter trays nearer to the door, then eventually put them outside under a covered carport.
The cats, she's got 4, were a bit confused at first. She made me laugh, said she watched them one day, they each got into a tray, outside, looked at each other, shrugged their shoulders and went in the flower bed. 😁 Good luck.