Galaxy Tab S4: Use of Screen-Off Memo
Screen off memo gives you the freedom of jotting down notes or ideas wherever and whenever you need. Simply pop the S Pen out and immediately begin writing. Once finished, put the S Pen back into the phone and your messages will automatically be saved in Samsung Notes.
To activate Screen off memo, go to Device in the Settings menu option and tap on Lock Screen. Then select Action memo on Lock Screen.
Press the button on the S Pen → Touch the screen while it's locked → Use S Pen to write → Touch Down arrow (to view more) → Touch SAVE IN NOTES
Pictorial representation of the above settings are as follows :