Drag the NE from either contribution wing and drop it into the affinity area.
To unlink any NEs linked by affinity:
1.
Rightclick on the NE in affinity and
2.
Select Delete Reference.
Deleting a reference to an NE does not delete an NE. It just severs the link between two NEs. Both the NEs, however, continue to exist. If you want to permanently delete an NE, this must be done from the cabinet.
Unlike the contribution relation, the affinity relation is not automatically reciprocal. That is, by placing one NE in the affinity area of a second NE, you have not thereby included the second NE in the affinity area of the first. The affinity area of each NE must be populated separately.
Affinity is populated separately for repository mode and for each object model. Just because one NE has an affinity for another in one mode does not mean that the two share any affinity in another mode.