Hello,
We currently have some development in progress and that user filter on the discount is not really simple since it will touch to a lot of files regarding the discounts and coupons.
So we do not have the knowledge of the exact amount of time required for the development, that's mostly why we can't provide any schedule for its implementation. Sorry.
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.