You can create “Custom Links” for those menu items – just put any url in them to add to the menu – then once in there, click the flippy triangle on the right end of the menu item and remove the URL and change the “Navigation Label” to whatever you want.
Thank you. I take it that in both cases, I need to delete the menu item in question and then create a replacement of a different type? So for example, to do what you are suggesting, I can’t change the existing menu item from a category to a link menu item?
Try just creating the new ones, then drag/drop the category items under them – wherever you want them to go.