WTH, why don't we have an interface for themes?

It might be a little too “big” for the WTH month, but I feel very strange to be forced to work in full YAML for themes, while a UI would be very convenient:

I think two different UI would be useful:

  • a UI to “manage” themes (create, copy, paste, delete) and manage the associated file structure and inclusion in config.yaml.
  • a UI to “define” a theme, with (at least for core cards and sections), all the main variables listed, their description (on click on an info icon for example), a way to change them and a way to view in live the effect of the changes. Of course, this should include a color picker interface to avoid defining all colors in hexa…

Duplicate https://community.home-assistant.io/t/wth-full-new-dashboard-to-customize-colours-in-ha/802555