Legacy animation with custom 1st keyframe value

I’m currently developing 2d hack’n’slash mechanics.
I already have 2 legacy animations (SwordCharge and SwordAttack)
SwordCharge is played while attack key is down and it’s increasing weapon rotation.z over time.

Next, when attack key is up, SwordCharge animation stops and SwordAttack is played.

However, it’s starting at rotation.z 0. Is there any way that I can make 1st keyframe’s (in SwordAttack) rotation.z custom value?

Now SwordAttack starts at rotation.z=0 and it looks atleast weird (sprite teleport?)

This is something that comes quickly in mind. Get the frame from where you release the button, and then continue your last animation on that frame. I dont really know how but i hope this atleasts helps a bit.