Thanks so much for letting us know where you get stuck. You can favorite more than one track. All you’d need to do is right click on the tracks that you want to select. Alternatively, you can use Ctrl+A (or Cmd+A on a Mac) to select them all.
With build 1.8 (882), I can now select all the tracks in my playlist, press the “heart” button, and they all get the “heart” label appropriately. Didn’t see a fix mentioned in the release notes. Perhaps it works on the SonicTransport (which I just switched to) and not on the Mac (which I switched away from), but at least for me it’s working now…