I have two sharepoint 2013 lists that have references to each other. It was one to many relationship. So "list A" has a lookup column that references several items in "list B" by clicking the checkbox in the column stetting "allow multiple values". "List B" has a lookup to a single item in "List A" (unchecked "allow multiple values" option). I would like to have a Microsoft Flow that is triggered after I create a new item in "List B" add the lookup to "List A" item to "List B" item.
In this scenario List A Items already exists. A user will create an item in List B and select an item from "List A". So now the link from List B item to List A item exists, but the link from List B item to List A item does not exist. I want the Flow that is started from the creation of the new List B Item to use the lookup to the List A item to update the List A item lookup to include a link to List B item.
When I create an action step in the Flow and choose the Flow option "Sharepoint - Update item" for list A, the lookup field to list B is missing.
Is there a way to achieve what I'm after in flow? It doesn't seem to be documented anywhere I've found.