Hey @lueurcollective,
You can create custom coupons codes via Online Store, however it would be up to the individual not to share the coupon. You can restrict coupons to a certain number of uses, or even a single use, then "refill" uses later as needed, if you want to give customers motivation to not share it.
You could also add their name to the coupon code as a way of customising it. I've included an image below as an example of how to set up a custom discount code. You can access online coupons via you Online Store Dashboard. From the main menu go to Items > Coupons. let me know if you have any questions!
