I need to implement static meshes placement on a level via Blueprints EventBeginPlay. Similar to how we drag static meshes through dragndrop to a level. And I need this static mesh to be saved in the editor after the game is running. Is it possible?
It is possible but you have to understand that the editor and your game are two different applications. This means that you have to build the whole thing (selection, moving, gizmos) from scratch for your game. You can probably dig into the editor code to figure out how they’ve done it but it wont be easy at all 
After that you’ll have to record the transforms of all player-placed objects in a save file and recreate them when the save file is loaded.
Its only once need. I found solution. Via EditorUtilityWidget