See the discussion https://github.com/agda/agda-stdlib/pull/1511#discussion_r650530794. I'd welcome any feedback from anyone else who has used it? https://github.com/agda/agda-stdlib/blob/358ad8bf673f0b292f5e5e86b50f0f6ec1d245cd/src/Relation/Binary/Indexed/Homogeneous/Core.agda#L32