Maybe there's still some hope the .ca Hub will eventually be improved. The ebay.co.uk update announced the addition of something called Self-Serve Coupons.
Is this the sort of thing you've been asking for?
Sounds like a darn handy tool to have available.
Again this is coming for the Brits not us lowly Canadians.
Excerpt from ebay.co.uk Autumn 2018 Update.
Self-Serve Coupons
Later this year, we’ll offer a new way to offer discounts to your customers, with the launch of Self-Serve Coupons. These promotional coupons can be set up by you in Seller Hub to offer a discount conditional to the use of the unique coupon code at checkout on any selection of your inventory. There is a limit on how many times the same customer can redeem the discount and a cap on the savings they can make.
The benefits of using these Self-Serve Coupons are:
Your unique landing page. A page will be created for your coupon, displaying all of the included inventory.
Easily shareable. You’ll be able to share your coupon and landing page on your social media and in marketing communications, as well as in postage inserts.
Encourages repeat buyers. The coupons can easily be used in postage inserts to drive repeat purchases to your business.
Track and measure. It’s possible to monitor the coupon performance so you can see where your buyers are coming from..