I'm developing a child theme of Twenty-Thirteen for a client. My theme contains a second navigation menu properly registered through my
This second navigation menu is fully working properly and just as expected.
However, as part of my design, I only want this second navigation menu to be a "single-level" menu; i.e., no children or sub-menu items.
I am able to remove any appearance of children menu items with CSS using a
display:none targeting the appropriate
.sub-menu item under this custom menu.
However, even though I have removed the visual possibility of sub-menu items breaking the layout, I'd like to stop the Admin from creating them in the first place. I don't want the client to add sub-menu items only to find they're not showing up. For nothing else, I'd like to produce a more robust theme, front to back.
I've searched Google, SO, SE, and the Wordpress site, but I cannot find out how I can block the creation of sub-menu items from the Dashboard. The research issue is stymied because no matter which search terms I use, I keep finding posts about people having the opposite problems... how to create a submenu.
I already have my own Dashboard page for custom theme options. Is there a way to customize the menu editing screen just for this one menu? A hook? Another idea for forcing a single-level menu?