HELP! What to work with on my horse today? Fun or serious ideas please!?

I’m working with my QH mare to build her top line and muscle. I have a 22-foot line, and a 12 foot line I can work with. Would disengaging her hindquarters at the canter be a good thing to try? (She does it well at the trot). Any other ideas for things to break up the monotony of boring work and also make her work at the same time?