Constants are data sources with a fixed value. Their value is not calculated while a process is running, but is defined by the user when creating a data flow.
Edit a constant that already exists.
Procedure
Activate the Variables and constants bar.
Activate the Constants tab.
Click Edit. The Edit constant dialog opens. Change the name and the value of the constant.
Alternatively, you can right-click a constant in the modeling area, and click Edit constant.
Click OK.
You have edited a constant.