The Output node's input field is shown when the output node is not expanded. (Tested on Windows 10)

Repro steps:

1. Create a new subgraph
2. Toggle the expand icon on the output node so the default Out_Vector4(4) is no longer visible.
3. If not already open click on the 'Graph Inspector' text on the top right bar and select 'node settings'
4. Select the plus icon to add a new input in the Inputs array
5. Observe

!Unity_TpwYJnR70O.gif|width=400,height=204!

Expected Result: The output node is expanded to display the new input field or the output node remains collapsed without a visible 

Actual Result: The new input field is visible and connected to the output node despite the Output node not being expanded.