While working on projects for different clients where I wasn't really allowed to upgrade them to the newest Unity versions, because of possible breaking and/or being out of sync, I noticed the inconvience of having to look through your program files to find the correct Unity version to launch.
I made a small tool that can both automate this task or make it very user-friendly. The program scans the given directory for installed Unity versions and allows the user to simply select an installed Unity version from the dropdown list.
Alternatively, a user or simply drag a Unity project folder and the corresponding Unity version will launch. I personally prefer using the dropdown menu as I know by heart which version the project that I want to work on is, meaning I don't have to search for its Unity folder.
I used this opportunity to get to use Windows forms for the first time and learn some new things.
Disclaimer: I made this tool before Unity Hub existed. I would recommend you use Unity Hub as it is regularly updated and from the same developers as the engine itself.