Glad that you are enjoying Tangent! Deformations will be available in a future update. IK bones can only affect other IK bones. So, if you have a chain of IK bones and you move the last child in the chain it will affect all other bones further up the chain but not effect the bone you are moving. What I do is create an additional bone and use that as a way to adjust movement. You should be able to add your own images in the trial version, I will double check this but I can also add the purple character's file included in the application.
For more information about mesh deformation I just published a devlog here.