@talksina @matze so my proposal for the summary would be
1. if excerpt is set, use that
2. if read-more is set use that
3. generate excerpt from content and use that
how does that sound?
the problem with a dedicated shortcode is, if you use it and have a post without read-more (maybe because the text is too short) it will show nothing. that's why I would prefer the fallback solution I mention above.