wiki/client/graph/admin/theme/theme-mutation-save.gql

mutation($theme: String!, $iconset: String!, $darkMode: Boolean!, $injectCSS: String, $injectHead: String, $injectBody: String) {
  theming {
    setConfig(theme: $theme, iconset: $iconset, darkMode: $darkMode, injectCSS: $injectCSS, injectHead: $injectHead, injectBody: $injectBody) {
      responseResult {
        succeeded
        errorCode
        slug
        message
      }
    }
  }
}