How can I load a level as a thread and after everything loaded, open the level in unreal engine?

Question

I need to open a map while playing in another map. but if I use open level(by Name) node, it will open level but everything is not loaded. it will take time to load textures and others. So I need to load a level as async task and after loading all, open the map. How can I achieve this? It may be either blueprint or C++ code.

If someone know this, please give me an easy way to achieve this.