You can backup you home-directory and add it back into the newly installed OS. Some of the more dedicated distro-hoppers will even have the home-directory on a separate partition, which they don't overwrite during installation and rather just mount into the new OS.
The home-directory contains all your music, pictures, add-ons and portable software. It also contains your configurations under ~/.config/
and local files of applications under ~/.local/
.
After you've reinstalled, you won't have all the same applications installed, but once you reinstall them, they should pick up the configuration from those folders and work as you expect. Sometimes, your new distribution/installation might use different versions of that particular software, so it's not guaranteed that everything works perfectly, but it does work pretty well.