Thank you. I can't seem to find the stickers in the Messages app if the value is set to {OS} or not set at all. My old Sticker App projects never had this key as it's introduced after. Seems like I need to change the value of this key to {Messages} for it to show up in the Message App. I still need to see when the sticker pack shows up when I set it to {OS} as the simulator probably don't show ? I tried mail and outlook and it didn't show.

Thank you for this information. I did read this information but seems like I missed reading about NSStickerSharingLevel. It seems like after I changed the value from OS to Messages and add all the app icons my stickers finally showed up in the messages. Are these requirements documented somewhere? The link above don't mention app icons being required?