Hi,
It's not the button "manage variants" which generates the variants but it's the action of adding a characteristic to a product which will generate the variants for that new characteristic.
If you change the characteristic afterwards, the button "manage variants" won't create the "missing" variants for the new values you might add to the characteristic.
The new product edition system that we are including into HikaShop (from HikaMarket) should propose an easier way to manage variants 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.