Reordering or inserting levels in the middle of a hierarchy has significant consequences.
First, changing the unique names for members of the hierarchy might invalidate MDX calculations that reference members of this hierarchy. For example, named sets created using the hierarchy’s levels or members might be invalid. Also, the default member of the hierarchy, which is specified by a unique name, might become invalid.
Secondly, any security policy defined for the hierarchy might be affected. If there are conflicting security policy changes for a hierarchy, a warning appears indicating that the conflicting policies must be removed and gives you an option to reconsider the level changes.