After we asked this question in the last Unreal Engine 4 Stream on 11.04.2019 about “[4.22 Editor Improvements][1]”, and the staff at minute 00:53:25 to 54:40:00 didn’t really know what is meant by this feature from the update notes of 4.22, we dug a little deeper.
We have actually found the feature listed in the Update Notes of 4.22. Unfortunately not in the UE4 editor, but in the source control history:
4 Jan 2019:
support update reference pose of skeletalmesh in engine
7 Feb 2019:
Back out changelist 4681906 of support update reference pose of skeletalmesh in engine. This caused more issue than it solves, so feel it’s a mistake to support this.
Soooo….lost in Nirvana i think? 
Screenshot from UE4 Source Control History:
Maybe you should update the Update Notes and the Feature Task “Skeletal Mesh Editor Improvents”, marked as done for 4.22 on the UE4 Trello Roadmap
Have a nice day