Oh is simple: 'Change Threads Prefix Inline' plugin and install -->
https://vborg.vbsupport.ru/showthrea...+Prefix+Inline
After you can create and add in Admin Panel -> Threads Prefixes -> your prefixes
When you create the prefix\es you have in the right of the page -> [Edit] [Delete] [Edit Permissions]
Click: Edit Permissions -> and set wich group is allowed to use it .
I attach 2 print screens for you .