Well, bridge support was not modified for yEd 3.12 and as such should still work the same way it did for previous version. (And indeed a quick test indicates it does.)
Bridges have to be explicitly activated in "File" -> "Preferences", tab "Display", option "Bridge Style".
However, not all edge types support bridges. Maybe you are now using such an edge style but did not do so before? In the "Edge Types" palette section only the first two styles ("Polyline" and "Polyline with Target "Arrow") support bridges. The types available in other palette sections ("BPMN", "Entity Relationship", and "UML") all support bridges.