I think this idea is cool and has been solved at least in my small country (Switzerland) with the following app on Google Play/Apple AppStore: https://www.profital.ch/ - I wonder if they will expand their “reachability” to other countries?! I will reach out to them if they have a website where “LAM Playground” could be usede to search for profits. Thanks for pointing out the idea!
Let’s see what they say 
Sidenote:
After you selected the discounted items you want, you can simply add the items to your favourite
We as a family used to use Bring! (which is also the maintainer of the Profital app) and now switched to WeNeed.ch which also supports Fooby.ch to import items directly from Recipes. Full story is available at: Cooking with Rabbit - #2 by huggi