Add-on to quickly change active theme not leaving 3D View.
If you want to pick a blender theme for your mood it could be tedious to open each time the preferences, select a theme from the drop-down menu, switch back to see its colors and repeat if you aren’t satisfied with them.
Instead with this add-on, you can select a theme in the sidebar list that shows all themes at once. You can use the arrow keys on the keyboard or Ctrl+Scroll to quickly switch between themes, or click on a theme name.