This product contains a code plugin, complete with pre-built binaries and all its source code that integrates with Unreal Engine, which can be installed to an engine version of your choice then enabled on a per-project basis.
Unreal has redrawn all the Windows's window elements, but they did not add window shadows. When you want to set the entire editor to a flat design style, shadows can help distinguish different windows effectively.
This plugin has hacked their implementation to bring back the system window shadows while removing their rounded corners. Additionally, it speeds up the response time when opening windows.