If this something really important, you could do it with autolinking and using the devtools to change to an “Or” instead of an “and” and linking by public id’s.
Then you have three relations. One normal ones, and one auto-linked one that has the content from both. Not sure how this scales or looks in practice, but its a potential solution I think. Didn’t test it.
Here’s how: Auto-linking via a to-many relation [workaround]