Quick question,
Do you mean constraints in a sketch or joints in an assembly?
Constraints in a sketch
Sketch constraints are always visible when the sketch is in edit mode. So if any constraints are applied to a sketch, they will be visble next to the geometry they are assigned to.
There is no way to disable a consraint, but if you would like to delete it, you can simply click on the constraint to select it and right click and choose Delete.
Joints in an assembly
All the joints in an assembly can be found under the Joints folder on the File Browser. You can click the little light bulb icon next to the folder to show all the joints or control their visibility by clicking the light bulb next to each joint.
To disable a joint, you can right click on the joint in the browser,or in the design window and choose Suppress. That will suppress the joint untill you right click it again and choose unsuppress.
I hope this helps. Let us know.
-Sachlene