You can easily edit your original post and overwrite or add the first chart attempt with your updated version. Just copy the new chart to your clipboard (select post to forums), go to your forum post, choose edit, select and highlight all the song code of the first version, select "paste" (not cut or copy) then SAVE. Done
It is better to edit your original post to include your playlist that failed to post instead of starting a new thread.
Users can not delete "thread-starter" posts (only admin can do that) but users can edit their own posts. )BOB