Moving actors between levels

Dear Community,
I am currently developing an rpg game and Im dividing the world into multiple maps, open world and cities, interior of buildings, and dungeons, I managed to create system to walk between the various levels with my player, but what if i wanted an NPC to travel between these levels? any way I could transport/move an actor/pawn between levels?

also is there a way to keep the level the player isnt currently in “alive” as in the npcs move around (i assume for this id have to create my own system where id just track the “position” of NPCs)

eg, (NPC leves his/her house and walks around the town, then enters another house…)

Thanks in advance.

Level streaming basically requires that the level you leave gets shut down when you leave it. Depending on the size of your levels, doing otherwise might be a bit much for many systems.