How can I fix a mole sauce with excessive cinnamon?
Clove or allspice can take it nicely over the top; sage and oregano can tame it.

This approach means to simply adjust the flavors of the sauce. Basically, if the problem you are having is that cinnamon is to cinnamon-y and distinct relative to taste, you can apply a flavor blur with neighboring spices (the clove, allspice, coriander, cardamom, cumin etc). If the problem is that you are finding that neighborhood of flavor to intense, you can round the palate by adding the herbs.

The other route would be re-scaling the sauce. Adding stock, oil/fat, peppers/onions, chocolate disks/cocoa, or other ratio constituents means you would need to re-up on the other constituents as it may throw off the sauce's viscosity. This may be preferable if you simply can't stand the cinnamon or its neighbors; or if balancing the spice/herbs would make the sauce too noisy.