I don't save a lot of fancy layouts and stuff. (I find it easier to stick close to the default layout because then my screen matches what I see on tutorials, especially since I don't get to spend a lot of time with Painter.)
Having said that...
Just install the new version. No need to remove the older one. I'm 99% certain it just updates the new program files, but your "shelf" and any customizations should carry forward just fine. I've never noticed anything missing.
I habitually download and save the installation files on my computer (disk space is cheap). That makes it easy to roll back by reinstalling an older version if I ever need to.
(P.S. When you update Designer, it detects your previous version and asks if you and to delete it, and I say "Yes" to that.)