I was curious and was able to determine what controls them. The GUIDs located in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\FolderDescriptions control those directories. One's that are visible with in the "ThisPC" sub menu will have a sub key called PropertyBag and in there a string value called ThisPCPolicy. Set to Show it will be visible. Set it to Hide and restart explorer and it will be hidden. My theory is that you would need to grab the windows SDK to generate a GUID for your custom entry and then create the appropriate sub key and other values