I play offline all the time so i think im okFirstly you need to have custom firmware running. This will enable you to extract saves.
Checkpoint/Edizon is what you need to run as homebrew.
Before you ask my switch aint hacked/jailbroken either look into soft modding with Atmosphere or SX pro hard mod. Each comes with their pros and cons.
Now here is a FYI it is very possible to get banned from nintendo online doing these so at your own risk.