I find that if you import the FBXs into a blueprint or as a level, it goes faster (and they are not only placed in content browser)
- Create a new empty level
- Create a designated folder for where to store the mesh/materials/textures etc for the import.
- Go to File → Import into Level
- Chose what to import
- Select folder location for the imported mesh and select OK.
- Scene → Import Options → Hierarchy Type → Create on Blueprint asset (or chose one of the others types)
- Change the settings you want
- Import
- When its done importing, the blueprint will open up.