The idea is to have the possibility to create sub-folders in the Catalog, on each tab : Maps, Layout, Styles etc. The ArcGIS Pro project organisation would be better, especially if we have too many Maps and Layouts.
Ex : in Maps I want to create a sub-folder names "country_maps" with inside all my country maps. Then a second sub-folder with inside all my regional maps etc. Same idea in Layouts and Styles tabs.