Hello,
Hidden settings are, as their name suggest, hidden.
It means that you need to access to your HikaMarket configuration database table in order to add an entry for that hidden setting.
HikaShop also have hidden settings and the process is the same (except it's in the HikaShop configuration table).
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.