I am a pro user with 5(!) mac with High sierra, please release updates also for this osx version!
The current version of Core Shell relies on lots of features only exists on macOS 10.14 or later, so it's not possible to make it backward compatible with macOS High Sierra (aka. 10.13).
But if you have installed older version that compatible with macOS High Sierra sometime ago, you can re-download that version by going to App Store and tapping the circle face on the bottom left corner of the window.