Spine team,
This is a major pain point in the user experience. Most software contains the ability to activate various features that are not enabled in the Trial version once the customer purchases the full version, making a seamless transition that does not negatively impact workflow.
I am a bit surprised that you have overlooked something that has been repeatedly requested for years; I've seen posts in the forum dating back to 2013 asking if this is possible.
Think about it - you have someone test driving your application, going through all the steps of creating meshes, adding bones, adding weights, creating an animation and they decide they would like to move forward with purchasing your software. Common sense dictates that they would love to be able to SAVE the work they invested in during the test drive.
Please integrate the ability to simply be able to save work once a person has gone from Trial to a purchased copy.