Agreed, this would be a good way to accomplish this if we decided to go down this path, perhaps with a bit more information around where the extension is active without having to go into the dropdown.
We’re not opposed to adding that functionality long term but it’s additional design and development work to modify UIs on the developer end (to choose valid combinations of active anchors – a problem that becomes larger as we add more anchor points) and adds cognitive load to the broadcaster.
If you have thoughts on compelling use cases for having an extension active in multiple anchors simultaneously, we’d certainly reevaluate the prioritization of that work.