The “LSS_LoadingScreenSystem” folder is part of this blueprint asset:
https://www.unrealengine.com/marketp…-screen-system
While the code plugin you might be referring to (available here) is a small utility meant to expose functionality to BP that allows the above blueprint system to query progress of levels that are being loaded (otherwise only available in C++).
You would need both for the full set of features, though, the plugin is optional - the blueprint system will work without it (but won’t be able to display a loading progress).
You could also use the free code plugin on its own to read progress of streaming levels in your project - I intend to release an example project in the community section, but have yet to find the time.