This seems like such an obvious thing that I can find literally nothing about this on the internet.
So, I installed SourceTree. I closed it, and now I want to start it again. There is no shortcut in the start menu, no tile on the start menu, it's not in the 'Recently added' of start menu, and not in the context menu of repositories.
I know it's installed for a fact because when I go to Window Settings/Apps & features then it's listed there with an uninstall button.
I found the exe in %LocalAppData%\Sourcetree but I really doubt this is the intended way to launch it.