Try going to Settings at the top next to Blueprints
Then under Scalability go to Engine Scalability Settings & change quality to low
After, below Engine Scalability Settings change Material Quality Level to low and that should increase program performance without hindering visuals too much. It will definitely speed things up, especially dragging large files onto the main map.
You could also change Preview Rendering Level to something of less quality, like Shader Model 4 or Mobile/HTML 5
I would also recommend in the NVIDIA Control Panel click Manage 3D Settings, add Epic Games Launcher as a program to customize, then in the drop down menu right below select the graphics processor: High Performance NVIDIA processor
Right click the Epic Games Launcher wherever it is located, and run as administrator.