Update tags from async onBeforePreview call in easy email plugin

I am trying to update tags after getting them from external url in github plugin zalify/easy-email
After user click preview it should update tags and change tags.

When I do it without async it is working fine example :

const onBeforePreview: EmailEditorProviderProps['onBeforePreview'] = useCallback(
    (html: string, mergeTags) => {
        const engine = new Liquid();
        const tpl = engine.parse(html);
        return engine.renderSync(tpl, mergeTags);
    },
    [],
)

but when I use async even without fetch it is not working.

const onBeforePreview: EmailEditorProviderProps['onBeforePreview'] = useCallback(
    async (html: string, mergeTags): Promise<string> => {
        const engine = new Liquid();
        const tpl = engine.parse(html);
        return await engine.renderSync(tpl, mergeTags);
    },
    [],
)

I think this is code part which handle the response by plugin PreviewEmailProvider/index.tsx

if (onBeforePreview) {
  try {
    const result = onBeforePreview(parseHtml, injectData);
    if (isString(result)) {
      parseHtml = result;
    } else {
      result.then((resHtml) => {
        parseHtml = resHtml;
      });
    }

    setErrMsg('');
  } catch (error: any) {
    setErrMsg(error?.message || error);
  }
}
setHtml(parseHtml);

I tried return fetch or return Promise but it is not working too.
I’m not getting error in console but tags not update in preview.