Hi,
Thanks for a great question
What I'd recommend is an install of AN os of the mobile SSD, set up (g)rsync to sync data back and forth, where the (say) external drive functions as "backup".
Instead of that, maybe considering a cloud (that can be trusted) to keep all data in one place. If that tickles your imagination, perhaps (your provider permitting) set up a cloud server at home...
Just some thoughts...
Have fun
Melissa