My question is similar, and unfortunately I'm not feeling very optimistic that this is supported in the current version of the SDK. I'm not sure where the official place to submit feature requests for the SDK is. If you find it, point me to it and I'll support your request.
You may have already gotten this far, but Order is an interface, and as far as I can tell has no public implementors. I think the only way to create one is from an OrderContext using one of the create*Order methods, and I don't see one for createTrailOrder nor as you've observed a generic one that takes Enums.OrderType, so unless an order can be modified to be trailing—which I doubt—I don't see a way using the public interface.
In fact, the only thing that takes an Enums.OrderType is a SettingDescriptor, which makes me think that it only exists for users to select in the strategy setup dialog. My inference then is that any study that uses it needs to manually implement a pseudo-trail by adjusting stops.
This is also heavily implied by pages 59-61 of the
SDK programming guide, which only talks about market, stop, and limit orders and uses a tone that heavily favors market orders.