This add-on is no longer in beta and can be considered feature complete and stable.
Changes from beta:
Fixup single prefix selection to include a 'none' option.
Rework detection of prefixes a user is not permitted to remove
On quick post thread forum, fix displaying empty prefix input when no prefixes are usable.
Add descriptions to template modifications
Move multiprefix filter and quick post thread template chunks to their own template
Make quick-thread feature only show prefix selection once post-thread form is expanded
Ensure prefix order is forced to match prefix display order to prevent unexpected flip-flopping of prefixes changing.
The front-end currently submits prefixes in display order, this ensures the backend enforces that.
Improve reliability of some template modifications
Improve uninstaller not removing all extra columns from some tables.
Improve installer upgrade code path to handle pre-1.5.0 versions
Fix upgrading from pre-1.6.x
Switch to select-toggle mode when only 1 max prefix is permitted
When moving a resource/thread to a forum which supports less prefixes than currently selected, trigger the pop-up informing the user that less prefixes are permitted
Fix creating threads/resources without a prefix