This is probably a bit overkill (maybe bloat), but it would be nice if we could have some kind of read-only property accessible to extensions (either under Scratch.vm or Scratch.gui that extensions can access. It would likely return "original" "highContrast" "dark" or "custom"
For example, changing icons to better match the color scheme, as seen above. It doesn't look horrible, but it might be nice to have