Just over a week ago, I applied this solution successfully, however…today, in a fresh project, I was unable to replicate the desired result, so I deleted my post declaring this to be a proper solution, as it appears UEv5.2.1 still does not recognize bones moved and keyed with regard to Additive Layer Tracks in a Blendspace. I am on the hunt once again for a solution to this…
(EDIT: Solution discovered! (Using Retargeted Animations in Unreal Engine | Unreal Engine 5.3 Documentation) & This post provided another step toward the solution: (Used persona to key new additive layer track and the newly keyed track does not show up in blendspace - #22 by Allonan)
Apparently, you also have to change the Translation Retargeting on the Skeleton for the specific Bone you have adjusted the position of to: Animation Scaled.