The Named Clipboards predate the clipboard history.
Presumably you know that Named Clipboards are like variables for clipboard entries and you can create them in the Clipboards preferences (or in other ways).
The Named Clipboard Switcher is like the Clipboard History Switcher, but for Named Clipboards. It has three variants for Cut/Copy/Paste, which just define what happens when you double click on an entry - when you are in the switcher and double click, Keyboard Maestro will copy or cut, and then put the system clipboard into the entry, or paste the entry depending on the variant.
The Named does not appear in the actions because it doesn’t fit and as I say, predates the clipboard history.
It’s not the best UI, but that is what it is currently.