code: private function applyFallback(array &$config, array $action, bool $skipLegends = false): void
      {
          if (\is_callable($action['fallback'])) {
              $action['fallback']($config, $action, $skipLegends);
          } else {
              $this->applyFallbackPalette($config, $action);
          }
      }
docs: Adds a new legend if possible or appends to the last one.