Since I open-sourced the code on GitHub, you are free to make a copy and modify it to your needs.
You can comment-out parts of the code where extra things (like dewpoint, wind barb, gust barb, visibility, heat-index/wind-chill are displayed) and just leave the condition icon and temperature for display on your GRLevel3 display. Leaving the condition icon would still allow you to mouse-over it to show the popup with the full conditions display.