To define your own placeholder, please follow these steps:

  1. Go to View > Master
  2. Go to the very first Master slide (it’s slightly larger than the Layouts)
  3. Insert a textbox or any other shapes to use as footnote
  4. Format and position the shapes
  5. Bring up the Selection Pane (Alt+F10)
  6. Select the shape
  7. Double click the name in the selection pane
  8. Rename it to “SP Placeholder Footnote”. This marks the shape as a SlideProof placeholder of the name “Footnote”. You can put anything after “SP Placeholder “
  9. Hide the shape by clicking the little eye icon
  10. Close the Master View and try the Placeholder button