[4.5.1] How to save changes to animated bones with Persona?

I’m using a walking animation that was created for a “stocky” man. I figured that the walk would fit this heroine if I just lowered the clavicles at bit and it works great. But I cannot save the final result. The bones come back to their original position every time I click to view the animation again into the viewer. I tried “Save” and “Save All” but the changes I made don’t stay put.

Bug ? Is there a “non-editable” flag that I must be weary about ?

Any help appreciated.