Often you have many similar, although slightly distinct queries you want enter into the verifier, and it would be nice if there was a "Duplicate" or "Clone" button for creating a identical copy of the query you just entered.
Also, why are empty queries not deleted?
Not a bad idea, although you can easily copy'n'paste the query.
As for deleting empty queries, people like inserting some space to visually group queries.
Understand the empty query argument, but I would still like to see the duplicate button implemented. Even though and paste is easy, duplicating is even easier.