The Published Inputs and Published Outputs Units are different from other Units. They can be seen as the "interface" which can be accessed by other Workflows (or Applications). Each Workflow has exactly one Published Inputs and one Published Outputs Unit. They are initially empty.

Adding a Published Input/Output

The steps are the same for Published Inputs and Published Outputs.

Go to the Workflow View.
Look for the Published Inputs Unit.

On the desired Unit, draw a cable (as explained in chapter → Cables) from the Input Port you want to add as a Published Input. In the screenshot on the left this is the String Input Port.
Hover the Cable over the Published Inputs Unit and release it.
A new Published Input will be created on the Published Input Unit.

Result

The Published Input has been created for the String Input Port.
Note that the Published Input has the same Name and Data Type as the originating Input Port.

Editing a Published Input Value

Go to the Workflow View.
Look for the Published Inputs Unit and select it.
Open the Project Panel and head to the Inspector tab.
You should now see all Published Inputs of the selected Published Inputs Unit.
Change the desired values (as described in chapter → Unit Attributes).

Changing the type of a Published Input is not possible. You have to remove the respective Input Port first and then add a new one.

Renaming a Published Input/Output

Go to the Workflow View.
Look for the Published Inputs Unit.
Double-click the Name of the desired Input Port.
The Name will be highlighted and can then be changed.
Press the enter key when you are done.

Removing/Rewiring a Published Input/Output Port Connection

Go to the Workflow View.
Look for the Published Inputs Unit.
Single-click the Cable which originates from the desired Published Input.
Press the backspace key to remove the connection.
The Published Input stays intact and can be rewired to any other Unit.

Removing a Published Input/Output

Go to the Workflow View.
Look for the Published Inputs Unit.
Click the of the Published Input you want to remove.

Reordering Published Inputs/Outputs

Go to the Workflow View.
Look for the Published Inputs Unit.
Hold the ctrl key.
Click the name of the Published Input and drag it to a new position.