Apparently older versions did allow deleting favorites. A quote from
this page says:
Starting with AM-DeadLink 4.7, it's no longer possible to change or delete bookmarks from your Internet Browser. Browser bookmarks should only be deleted within the browser user interface, not via external tools.
A full explanation can be found
here and it says you can try the 4.6 version instead.
Apparently the coding for favorites and such has become more complicated in browsers which makes it more difficult for external software to modify and delete them. You could take a chance and try to find an older version (4.6) but the links I looked at for it didn't look too safe so I'm not going to provide one here. Also, it may or may not work correctly.
There is a reason that function was removed in the software. Backup before trying it if you want to do that.
Edge now has a built-in function to remove duplicates:
That still leaves no way to remove "Dead links" that I can think of. Maybe someone else will know.