I’m agree with Framecount,
currently I look at the video series “Skeleton Assets” and have problems with version 4.15 to recreate what is shown.
Videolink: Skeleton Assets
example: In video 02 “importing, sharing, …”, if I import the couchknights character, I get the message “failed to merge bones”, if I click “no” and try to create a new skeleton for the charakter (explained later in the same video) with double click the skeleton-mesh, I can’t create a new Skeleton, just “… hierarchy doesn’t match with skeleton anymore. would you like to regerate skeleton”. If I click yes, the other characters with the default skel-mesh doesn’t work anymore.