Added somes property, SubIndexSkelFormat + AddSubIndexSkel + SubIndexSkel, will define actual Sub-Index of a SkeletonDict[ n ][ ? ] and will also define possible type to use in any new attemp to add a SubIndex, with AddSubIndexSkel... Like Adding Lib to SkeletonDict[ n ] and assuming its a list type we need to store any lib. This Will imply using SubIndexSkel=Lib, SubIndexSkelFormat=list, by calling AddSubIndexSkel it will create a SkeletonDict[ n ][Lib]=list()... This require to protect property AddSkeleton, VarDefSkeleton, and saving current SubIndexSkel internally, and restoring it at the end of the property... see code for this modification