Location of Registry Key for Dropdown Menu

Greetings,

I'm seeking assistance in locating the key for the dropdown menu in Explorer. My aim is to streamline navigation by eliminating unused folders. While I've come across numerous resources for customizing the navigation pane on the left, I haven't found any for the dropdown menu.

Is anyone familiar with the registry keys associated with this? If so, could you provide guidance on adding a dword to hide the unwanted folders, or is deleting the key the only option?