i can't speak to the 12 series, but i've done a couple with the iphone 8.
unfortunately, i haven't fully committed the process to memory so i'll say what i can, but may need some others to fill in the gaps.
in the case where you don't have the original screen to read, you will need to connect the phone to the v1se via the lightning cable to the USB port on the top of the programmer - not sure if it's necessary to have the programmer to the PC via the USB-C port.
unlike doing a screen-read / screen-write action, you don't use the Reading and Writing functions. i think it's one of the other functions that you have to "scroll" to with the main button.
i may actually be working on an SE2020 screen swap, so i'll try and make note of the steps (as if i didn't have both screens).
i'll update this response if i have something useful.