Allow users to copy and paste custom form fields so you can make new ones that utilize similar options in other forms without overriding shared fields. Or allow the user to "hide" certain fields on various forms in different ways so we can use similar things in different forms but add or subtract different things. Example we have custom forms that we use in the US and similar in Europe, we both have similar project types that we do but in each of the regions, we have ones that the other doesn't offer.
