Can you verify that you've installed the Designer updateSiteOpenNTF-designer.zip?
(that is, not the runtime updateSiteOpenNTF.zip)
In Designer, in the Help menu, About IBM Domino Designer, Plug-in Details,
check for a Plug-in with ID: com.ibm.xsp.extlib.designer.relational
That's the new design-time-only plugin containing the JDBC Driver Plug-in Wizard.