They used to have a separate star button in addition to the like button that was exactly that, but they took it out years ago. It would also add the song to a separate list in your library called "starred songs".
When they axed the feature, all the started songs got automatically added to a new playlist called "Star" that I still use today as a workaround, I just add new songs I enjoyed to it to keep track of them, and just throw it on shuffle when I'm not in the mood for anything specific.
When they axed the feature, all the started songs got automatically added to a new playlist called "Star" that I still use today as a workaround, I just add new songs I enjoyed to it to keep track of them, and just throw it on shuffle when I'm not in the mood for anything specific.