Using a Blutility to modify an Actor in a Streaming Level doesn't make it dirty and prompt it to be saved.
This was reproduced and tested in 4.19.2 (CL-4033788), 4.20.3 (CL-4369336), 4.21 (CL-4435822), and Main 4.22 (CL-4448303)
Results: The Editor does not recognize that the Actor was modified and consequently does not offer the level for saving
Expected: Any scripted change should mark the Level of the changed object dirty so that it can be saved
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-65106 in the post.