One possible synonym for un-pins could be 'detaches'. Detaching refers to separating one object from another, much like how you can detach pins from an object. Another synonym for un-pins is 'dislodges'. Dislodging denotes removing something from its position or location, which is similar to how un-pinning removes a pin from its place. A third synonym is 'uncouples'. Uncoupling refers to separating two things that are usually joined together, again, making it another fitting synonym for un-pinning. All three words describe the action of removing or separating something, which makes them excellent synonyms for un-pins.