Happened to me with 4.23.1 rather frequently when you delete referenced content, this even for a few files can take extensively long, making me quit the editor through the windows task manager. Deleting the cache folders as outlined above fixed it for the most parts, some errors remain though …
Update,I figured out a way to resolve it, explained here Failed to load Outer for resource on opening a persistent level - Blueprint Visual Scripting - Unreal Engine Forums