With IBM Engineering Lifecycle Management (ELM) 7.0.2, the way backlinks are discovered in ELM applications has changed.
Previously, it was enough for Windchill to associate a Change Management artifact  with a Global Configuration (GC) to allow ELM Configuration-Management-enabled applications to discover backlinks . Now, not only the Change Management artifact needs to be associated (linked) with the GC, but this GC itself must also be linked with Windchill... in other words, a double link is required.
This double link can be managed automatically by Windchill. What this means is:
Synchronization requiredmessage in the Global Configurations table. The
Synchronize...button opens a wizard to attempt linking with the remote GC.
Note that in order to display the Global Configuration Application picker dialog, the friending of a Global Configuration Application must have been done in Managing Friends.
Note that the synchronization between Windchill and GCM only occurs with ELM 7.0.2 or more recent versions. However, in order to allow creating links between Windchill Change Management artifacts and external resources that participate to a GC, this GC needs to be declared in the Product administration first, independently of the ELM version.