Question: Is DISTINCT supported in DESelect?
Answer: DISTINCT allows to return only unique rows in your results. DISTINCT is a 'dumb' way of deduplicating, as you have no control over which duplicate row is removed from the results.
DESelect allows to do prio-deduplication, in which advanced rules can be set up to on how to handle with duplicates. You can read all about the prio deduplication options here.