Dear Eleanor
I did not "100%" catch your problem. Generally. anything is maintained in e.g. CG02 and/or CG02BD.
Here you have some options to "simply" copy Data from "A" to "B" (A = Spec number, B = Spec number); as long as the property involved is the same etc.
Therefore: let us seperate the "SDS" display topics from the"maintenance" topic of a specification.
E.g. in most cases SDS layout is designed like. if a "spec listing" is used and more than one spec is listed there than the data for "all" of the specs will show up in SDS. You need normally not to maintain per spec an own data record (but sometimes you must do it like that).
Regarding": " there was a way to transfer maintained values you selected that were.." you did not describe this in details. Does the process use SAP standard or was it done by an "customer enhancement"
So with out a more "practical" example I can not help
C.B.