Instead of using create Instance level, use Create Instance. This is an old Kismet function left inside the engine from UDK3.
target is streaming level, give it a unique name ( like appending a random integer to the level name. When you set should be loaded and should be visible to true, it will load on the level, and unload if you set them false.
Important thing is, this node won’t be visible unless you turn of context-sensitive on bp node search.
Also, this note will always give a warning since it is so outdated but it was still working on 4.21 with no problem. Remember that because of that warning bp nativization may or may now work, I never tested it with this node.