You are in the Interactive Planning and have already loaded data. You display the initial column in your Planning Book. A context menu opens when you now right-click on a cell in the initial column. In this menu, you can select the "Display note" function. If you do this, create and save a note text, you get the message /SAPAPO/SDP072 (which states that the note could not be stored).
Related: Display Implemented SAP Notes in the Note Assistant
Usually you cannot store or read notes in the initial column. There is therefore no point in creating notes here.
Once you implement this note, the function for displaying notes in the context menu is hidden when a cell of the initial column is selected.