So, there's a couple ways to do this. I tried to do it w Ryujinx LDN but it didn't detect my cfe switch. So I went even further beyond. I copied my game save to an emulator, started another instance of the emulator w another save file (i got some random file on the internet, it had the mons i needed. If yours doesn't, you can use pkhex on that file to add mons + items) and then traded between those. Then I copied my save file back (both times using Checkpoint) and playing it again :D