Every time I create a Quarry query, I need to type enwiki_p. This is a minor irritation for me but potentially show-stopping for a new user who can't guess that name.
Could the database name default to the user's home wiki, or a settable preference, or to the database used last time? Alternatively, could enwiki_p appear near the top of the long list of unlikely options that appears when one starts by typing "e"? It's almost certainly the most used database.