How many data connections is Toad using for the attached example? I would guess 3: Workflow 1 uses a query builder, Workflow 2 uses a sql editor, and Workflow 3 uses a sql editor.
Duplicated your workflow with my own queries, using Oracle...BTW, it's WF1 uses Editor, and WFs 2 and 3 use Query Builder.
Using Spotlight on Oracle, looks like four connection threads are used in this scenario. Guessing one connection for each of the WFs, and one for overall management? Quest's Dev team may have extra clarity.
I would imagine that Toad Workbook performs similar connection management in other RDBMS-flavored platforms.