Users can not delete "thread-starter" posts (only admin can do that) but users can easily edit their own posts.
If you choose to post edited charts, it's easiest when you re-post your (edited) chart or playlist as an edit to your original post. Instead of multiple posts and versions, you can easily edit your original post to add the missing material or overwrite the first chart (or playlist) with your updated version. Just copy the new chart (or playlist) to your clipboard** (just 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.