Unfortunately Poedil88 is correct, Spine Ess doesn't have free-form deformation. In fact, it doesn't have IK constraints either... It lacks quite a few standard features that are found in other programs. You can see the compare list on the right of their page here: https://esotericsoftware.com/spine-purchase
I too was trying to purchase spine (they don't accept paypal), but after using dragon bones and all of it's powerful FREE tools that are in it I decided not to afterall.
Instead, I've downloaded the runtime code for C# and C++ and am currently working on a solution to get dragon bones json files loaded into game maker. Currently C++ is what I've been working with, but I'm also looking for an alternative as I don't really want to use a compiled DLL as it limits the export options.