briefly spoke about this with @aleventhal today (cc @mfreed7)

from what i understand there have been talks about creating an aria-details relationship, similar to the one defined for popovers, if authors were to use CSS anchor positioning to associate elements with one another.

this may be useful / help provide a baseline of information for instances where an author has decided to 'tether' one element to another in the UI, but not provide any meaningful semantics to programmatically communicate this relationship.

if this were to be done, would expect this to have similar logic to popovers, where the aria-details relationship is not exposed if the elements are direct accessibility siblings to each other. Additionally, it might make sense to not expose this relationship depending on the roles of the elements that are associated. e.g., if someone were to use a role=tooltip and/or had an aria-describedby association already made, then the aria-details association would likely just be extra noise - so maybe don't do that then.

also, might be worth reiterating that if someone were to use an aria-details="" on one of the elements, that the details relationship should be considered null - as that should be considered a signal from the author that they do not want there to be a details relationship, for whatever reason.