As stated there is no option to filter by UR in using the "Best Backlinks" filter backlinks/referring domains report.

This doesn't make sense - as we're trying to identify the Best Backlinks as opposed to links from strongest domain.

Purely from a PageRank/authority perspective, your "Best Backlink" is ideally one from a page with organic high traffic + high amount of link equity/pagerank (what ever you want to call it.

I'd rather a link from UR 20 + DR 40 rather than UR 0.5 + DR 70

This feature only really captures half the equation.