Filter Threads By Thread Prefix - MyBB 1.6 Only

[Kiero]

How do I go about making a dropdown box for selecting the prefixes, in both the thread list and when making a new thread?

Ie:


But so it shows all the prefixes

And also so it has a dropdown instead of a listbox in the new thread page (unlike this)

Thanks a lot for how much xThreads contributes to MyBB