You can take them apart but unfortunately you can't simply make the stud longer unless Morton actually sells just the stud part seperately which I doubt. If there's room, you might be able to cut off the stud, drill & tap, then screw in your own stud.
If that's not possible or if you need a length that no one makes, you can buy a female adjustable handle then make your own length stud using all thread or a long set screw or turn your own.
For example, I needed a short handle with a larger size & longer stud that no one made. So I got the size handles I needed with threaded holes, then I used long set screws cut to length then rethreaded one end to fit the handles. Use red Loctite & they have been working great for years now.