Hi
It might be worth exploring why you want a trial version of 12.6?
If it's to open a copy fo source code in that version so you can have a look at it, then you can just open it in PB2022r3 and migrate the code then view the code in that IDE.
If you are looking to make changes to the code without having a legitimate license then that is not going to happen. The only way forward if you want to make changes is to migrate the code to PB2022R3 before making any changes.
I hope that helps
David