Groove Clip (follow pitch) question: Why only major chords?

Enjoying the the Groove 3 tutorial "Sonar Advanced".. 
Its clear to me now how to make the loop/clip follow different pitch/chords through Markers.. however, I am not sure how to handle minor, 7th, 9th chords.
Example/scenario: blues based song
Working with B3 Hammond type of loop and I want it to follow the 12 bar blues chords (A7-D7-E7).. i can go to marker and change the key, but can I do something so that it play D7 instead of D (too much to ask?)... i see only Major keys in that list.. 
I am sure my understand of this is wrong somewhere.. any help would give me more control over loops.
 
Thanks
Shahed