Can move individual mesh instances of a regular instanced mesh component in the blueprint editor, but not hierarchical ones.
Originally reported as a pull request in [Link Removed], but we rejected their fix.
The existing handler should be calling UpdateInstanceTransform() rather than updating the PerInstanceSMData array directly, which would work for both component types.
Add a hierarchical instanced mesh component to an actor blueprint
Add some instances to it in the details panel inside the blueprint editor
Click on instances in the blueprint editor viewport and try to move them around
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-29357 in the post.