simplest way would be to read wordpress docs on hooks: http://codex.wordpress.org/Plugin_API
I would put the hook into my spFunctions.php…
quick example:
add_filter('sph_post_editor_header_top', 'my_submit_buttons', 10, 3);
function my_submit_buttons($out, $spThisTopic, $a) {
#output buttons here my adding to $out
return $out;
}
so basically, when sp is at the top of the editor form, it fires that hook (sph_post_editor_header_top)… anyone can hook into that location and add stuff… or remove if you are handy with regexp…
you can grab the button code from the sp post form… but beware, you may have to hardcode the text strings and may not get math spam enabling of the button (not an issue if not using math spam)