IntelliJ certainly enjoys making simple things difficult whenever and wherever possible. Depending on which version of the snap you installed, you’ll need to launch the application from the command line.

If you installed the community edition, do this:

intellij-idea-community

If you installed the “ultimate” edition, do this:

intellij-idea-ultimate

So long as the snap was installed with the --classic option, you’ll be able to add IntelliJ to the launcher by going to the “Tools” menu at the top of the UI, then select “Create Desktop Icon”. This will resolve the issue of having to open Terminal every time you want to launch the application.