Sandbox level switching (without loosing any progress)

Hello.
I’m working on a sandbox game. I want to use multiple levels, but while loading levels the normal way, they reset and I don’t want them to. So for example when the player builds some kind of building or collects an item, the building has to stay and the item cannot just respawn when you switch levels.

If that’s not possible then I’m okay with putting all stuff in one level, but if it is, please let me know.

I think you’re looking for Level Streaming