Question for folks who have messed around with visiting/raiding other islands: Could you use islands to store items and transfer them between save files?
You can't.
Visiting a save doesn't alter it no matter what you do. The game also reloads your last-loaded save when you end a visit, so you lose everything including XP and all items picked up while visiting. You also lose all your progress since you last loaded the game, even the stuff
prior to the visit, unless you saved over the last loaded save right before the visit. (Not recommended, it's best to save-and-reload because you might pick the wrong save to save over.)
The only exceptions are tokens earned during a visit; the game will take note of the tokens you earned and put them in a crate next to you when it reloads your save after you're done with a visit. A side bonus is you get a free crate to use as a container.
And for obvious reasons never,
ever save a game while visiting another save.
Just wondering if there is a way to save time on gathering resources when starting a new save file if an update requires it.
Just cheat the resources back in using the /get command.
Also generally speaking the game is quite good at maintaining backwards-compatibility over updates anyway provided you don't immediately jump into the buggy new versions (the ones ending with a .0 when a new milestone update is released). And don't use mods. And don't jump back to an older version after moving your save to a newer version. The game effectively rebuilds the map from scratch on reload (which is why saving and loading takes forever).
Bugged event flags are rare on patched releases, and if they occur can be fixed with console commands or save editing anyway.
Personally I only start a new playthrough if my save file gets too bloated and loading takes forever. Or if I want a new challenge or fresh playthrough.