Our Markua support is still in early beta, and our support for Markua's index entries is not implemented yet.
We have already added support for indexes to the Markua 0.29 beta branch, but we are about 1-2 months away from deploying it. So, expect to see index support by the end of August 2021. When we do deploy it, they will work like this:
In the meantime, here's a Help Center article that may be helpful on this matter: