I don't have this option in my Note phone so it maybe a Region dependent option.
However there is another route @nipper10
Take your photo.
Look in Gallery and choose the photo.
Tap on the Pencil Icon at the bottom.
Press the Stickers icon.
Current Phone > Samsung Z Fold³ 5G.
@nipper10: I had a look into this for you, and the Watermark option in the Camera Settings menu (Camera > Tap the cog symbol) becomes greyed out when you have the 3:4 48MP aspect selected. If you choose 3:4, 9:16, 1:1 or Full then it will be available for selection. I hope this helps. ^AL