How do I make thread prefix default, i.e. when a member posts, he don't need to select from the thread prefix.
e.g. If he posts in health forum with subject: Eat apple
Then it's subject will become [Health forum] Eat apple
Here [Health forum] is the thread prefix
Open ./newthread.php file and find;
$mybb->input['threadprefix'] = 0;
and change 0 to the Prefix ID number you wish to use it as a mendatory.

If I have more than 1 prefix for the more than one forum then?
i.e.
[Health forum] --> default on forum Health
[mybb Forum]--> default on mybb help section forum
With the above solution, its not possible. It require some more core file edits.
Sorry for bumping an old thread, but this is possible.
I've done it like this:
$plugins->add_hook('datahandler_post_insert_thread', 'myplugin_defaultprefix');
And then this:
function myclanmanagement_testthing($array)
{
$array->thread_insert_data['prefix'] = 1;
}
I achieved this with this simple thingy, not sure if it's the most proper way.