To show all inputs to one output you must configure and add the set to the Paths tab.
To create a set showing all inputs to one output:
In the Paths tab, from the Edit menu, click Add Set of Paths. The Add Path Set dialog box appears.
Select the Inputs and Outputs radio buttons.
Click the directional arrow to point it left.
Choose the desired output endpoint in the To list box.
Select all inputs (all starting points), by Clicking on the Select All button under the From list box.
Click OK. The set showing all inputs to one output is added to the Paths tab.