Abandoned Cart based recommendations

Hello everyone, 

We want to implement a use case based on the cart of the user. 

The idea is to recommend items based on the user´s items in the cart. We can do it using the 'item-based' algorith type, "Items with similar attributes" Algorithm and "Current item" reccomendation Key like following:

It worked fine. We were able to get proper recommendations around one item. We tryed this approach with several items using a custom token "profile.lastItemAddedToCart" where we save the IDs of the user's cart items like so: "id1,id2,id3..."

As you might understand it did not work, so, my question is: is there a way to make it work? We would like the algorith to be item-based with a item with similar attributes as we can manipulate the recomandation with the content similarity fields:

Thank you in advance.