Benefiting from the Relational System - Mastering phpMyAdmin 3.4 for Effective MySQL Management - page 189

Defining relations
As we have already defined a relation with the Relation view , we will first see how
to remove it. The Designer does not permit a change in a relation. However, the
Designer allows the relation to be removed and defined.
The question mark icon displays a panel that explains where to click, in order to
select a relation for subsequent deletion.
Let us click on the relation line to select it. We get a confirmation panel on which we
click on Delete .