Hi Yatin,
thank you very much for reaching out.
Unfortunately rigging is not supported by UMotion. My goal for UMotion is to be the best animation editing software for Unity as animating inside a game engine has lots of advantages compared to conventional approaches where you animate inside an external 3D modeling application. This is because animations often interact with the game environment thus is more time efficient when done directly in your game's scene.
On the other hand, rigging is a very isolated task that doesn't have much advantages when done inside your game's scene. That's why I currently don't have any plans on implementing rigging features into UMotion, I'm sorry.
Please let me know if you have any further questions, I would be happy to answer them.
Best regards,
Peter