Hello,
Since tax rates/categories are shared between every vendors, they cannot be allowed to add or edit them.
So, HikaMarket does not include the interface for tax edition since it's some kind of advanced configuration ; so it's only available in the HikaShop backend.
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.