Using Blender 2.9.
I have an animated armature with only two frames. The armature at first frame matches the rest position, while the second has two bones rotated. Now, I'm trying to achieve a possibly unsupported operation.
I want to set second's frame pose as rest position, without causing the same effects on the first frame as well (ultimately, to prevent loosing that position). I understand this isn't a straightforward goal because poses are "forward"-relative to the first (you may correct me if I'm wrong). In fact, when I try to do it, Blender throws the exception "Actions on armature will be destroyed by new rest pose", and replicates the rested pose to the first frame as well.
Is there a way to achieve this, even if it involves reversing the animation so that the original second frame becomes the absolute source of the transforms for further animation frames? If there is a compatible addon with latest version which exactly allows to do this, that'd be fine.
Note when I apply that pose as rest position, I can't restore the old first frame's position anymore, even when I copy-paste pose from another Blender instance with the file without these temporary changes.
(The model is about hands for a viewmodel)