ExcludedAssets are assets which are excluded from your final packaged game. They have no influence on the Cleanup process.
This process is very helpful if you have a certain development-only assets, e.g.: BP_PressEnterShiftWin which you want to keep in your project/level to simplify development experience but you want them automatically remove from the final package.

Select the assets you want to mark and use the asset context menu to Mark as Excluded.
Select the folders you want to mark and use the folder context menu to Mark as Excluded.
During the cooking process, the Clean Project Subsystem will log all the assets excluded from the final package:
[2023.02.24-09.18.58:931][531]UATHelper: Packaging (Windows): LogCleanProject: Display: Modifying content to be cooked
[2023.02.24-09.18.58:952][531]UATHelper: Packaging (Windows): LogCleanProject: Display: /Game/StarterContent/Props/SM_Chair.SM_Chair is excluded from packaging and will not be included in the final build

You can view entries from Excluded Assets in the Settings page. Navigate to Project Settings → Out-of-the-Box Plugins → Clean Project and remove unwanted assets from Assets Excluded From Package and Folders Excluded From Package.
