Transforming Bones, closing Persona will reset the bone transforms!

Hey, I created a blank copy of the heroTTP and I want to make him sit, without animation so just some skeleton transformations, I can do this, but when I close persone it will not use this for the skeletal mesh and it has been resetted to the T-Pose. I’m not that familiar with Animations and some stuff like this so can you help me?
Thanks!

You cant transform the bones in persona -> you will have to do it in your 3d program Probably you can somehow move it into the right position in the anim graph with a transform bone node e.g In this example I move the upper body of my character with the mouse