File > Options > Graphics > Annotation > My Footnote
Specify information to include in a custom footnote on all graphs. The changes you make to the defaults remain until you change them again, even after you exit Minitab.
Information to include in my footnote
Project name: Display the project name.
Worksheet name: Display the Minitab worksheet name.
Date the graph was last modified: Display the date on which the graph was most recently modified.
Time the graph was last modified: Display the time at which the graph was most recently modified.
Custom text: Enter any text that you want to display in the footnote.