
For any app to be launched from favourites in Ubuntu, it needs to have a ".desktop" file that can be pinned to the Ubuntu's dash as favourite. This helps in quickly launching the application at the click of a button from Ubuntu's dash in desktop.
Spring Tool Suite IDE (aka STS) for ubuntu comes as a zip file that needs to be extracted to a custom location. Inside this extracted directory you'll find a linux/ubuntu executable file by the name that goes something like SpringToolSuite4.