For the asymmetrical case (i.e. parent/child, but not sibling), we could add view:Pointer, only applicable to Searches of form {"plus": ["field", "_self"] }. It offers an "add" link, and when it's edited, an edit interface similar to Pointer (but the existing items aren't editable), with a box where items can be added. When Save is clicked, the new cards is created, with newcard+field being filled in with _self.