Unreal Engine: Loading Static Mesh Performance Issue

I have a high density model (~50K static meshes). I need to load it in UE4 and visualize all pieces.

Problem:
Currently I setup one actor for each static mesh and store them in one map. The time to load the map in the Editor takes about 2 minutes, too long!

Target:
1) We want to load the map in less than 10 seconds for the first time;
2) When transferring back to this map, loading the map in less than 1 second;
3) Could preload the content when starting the APP (loading screen);
4) Platform: i7 CPU + 16GB Memory + NVIDIA 2060 + SSD disk;
5) Merging static meshes is not allowed;

Model:
1) All static meshes are stored as uasset files;
2) there are about 50K uasset files;
3) All assets file size is about 6200MB;