yes, what you described is what I’m doing I think. The parent of the object shown above is rotated to face a direction, and then I want it’s child object (attached to the spring arm) to rotate relative to the parents transformation.
It is certainly possible to do this using trigonometry, but alas that is why I thought I’d ask on here before I hard-code it myself. it just seems so simple that I’m surprised it’s not natively supported by UE.