I have an entire save system and menu set up and can properly save my inventory and location of my actor, however the level that gets streamed when entering a new building is not saved but the location of the player is, causing the player to fall out of bounds. I got other problems like items in the level not saving when picked up and destroyed but saving in the inventory causing a duplication glitch when loading back into the main level and picking up items again, and also currently falling out of the world before it loads in. I have made a mess of my blueprints trying to fix these issues so if you want to dm to fix this I dont mind.
May not be the most practical solution, but what I did to work around the falling out of bounds issue was to spawn a basic block under the player while the streamed level loaded, then destroys when gameplay actually begins