Trying to manipulate menu items prgramatically

Hello,

I am using the Twenty Twenty-Four theme and added a Login/Logout menu item via the editor, and wish to add a Registration menu item that only displays for visitors who are not logged in.

There does not appear to be a built-in block for this, so I am trying to add it programmatically but so far nothing I have tried works. I don’t want to use a plug-in, but wish to code it myself. I don’t think what I am looking to do is odd, so I am very surprised that I cannot find a solution.

Is what I am trying to do possible and if so can someone please point me to some working example code?

Thank you!