If I want to update the game, I just need to drag my old save to the game's updated folders, right?
Btw, I'm playing on Joiplay (10.0.2 to 10.2)
In theory, yeah.
But...
Sometimes there's an announced engine change that recommends/requires fresh start.
Sometimes there's change to some of the items, which might break them, or break the save when they're equipped.
Sometimes there's change to location or NPC which might break the save if you're there/with them.
Sometimes there's unannounced bug that can break any of the above.
Even on succesful move, it's generally recommended to rebirth ASAP, making new Lona "native" to the new version.
If you're on Joiplay, the new game version might no longer be compatible with the Joiplay version.
That's assuming you're not modding anything which would add more points that can break.
So give it a try but don't be too surprised when it might not work.
But like, once you've been playing for a bit, you'll know where to find unique items, you'll know how to grind money or rebirth count, or just console cheat it. Don't get too attached to your save, transcend the material and become one with Lona as a concept.