This pane is more than a scratch pad to keep track of what happens when function buttons are pushed. It also interacts with the JMRI throttle.
When you use the roster pull-down on the JMRI throttle to select a loco from your roster, the function buttons will be marked with the descriptions you have entered for those functions in this pane.
You may also set the text in the Function Labels from the button properties of an active JMRI throttle when you save them to the Roster. Subsequent uses of the throttle will use the new labels.