After doing some digging on performance, I found that most of the time was spent on repeated calls to StaticFindObject deep inside FPrefabGEditorAdapter::LevelFactory_FactoryCreateText::Local::ImportProperties. By caching the results of calls to StaticFindObject, I was able to bring down Apply times by an order of magnitude (from minutes to seconds). I’d be happy to send you a diff, if you want, or if you have a github repo, I can submit a PR. Cheers!