How can I insert new fields within an existing admin form via plugin/hooks?

[kh99]

Unfortunately, you can't. The adminCP works differently than the forum in that it doesn't use templates and just outputs html as it goes along instead of once at the end, so there's no chance to change it via str_replace() or anything like that. The best you can do (without editing the file) is to use hook forumadmin_edit_form and add it at the end. (It's fortunate that forum.php has hooks at all, a lot of the adminCP doesn't).