This is a small addition that will make life a little easier for some people.
A Great Bass recorder is usually notated the same as a bass recorder: Bass clef sounding an octave higher than written. It is an octave lower than a tenor recorder, so its lowest note is written with two ledger lines below the bottom of the clef.
A Contrabass recorder is an octave below a bass recorder, so it is notated in bass clef at concert pitch. Its lowest note is the F on the bottom line of the bass clef.
I’m sure that it’s easy enough to create these instruments manually, but as they’re a pretty normal part of a recorder consort, why not add them to the default list?