Keep data on old switch?

[Mura]

just gonna get straight to the point; I bought an oled switch recently and want to do a system transfer. however i'd like to keep my new horizons data on my OLD switch.. i can only assume the data gets transferred when doing a system transfer, but im not confident since, y'know, nintendo.. so, is it possible to keep the data on my old switch? would i just simply do a system transfer and then move my island back onto my old switch? i tried looking for this info but i can only find info on cloud saves. if this isnt possible, i have a friend who will let me move my ACNH save to his switch, and then back onto my old switch once i finish the system transfer. but im annoyed at how vague the information is about transfers.

maybe it really is simply and im overthinking it, but i just wanna confirm this with someone before i try anything lol thanks

 

[Mura]

 

[VanitasFan26]

I'm afraid to tell you this but once you make the transfer to the new switch from the old switch the data that was on the old one is deleted. There is no way to recover it. So you cannot have 2 islands at the same time on both switches.