If you're talking about the Body Composition feature in Samsung Health, than the new icon looks like this (see attached) and can be added to the menu via the Edit Home option in Settings.
I hadn't noticed this yet but you are correct, weight by itself is no longer an option for the Health home screen. It seems to have been moved into the function Body Composition. I can only speculate that the reasoning here is to get people focused on their overall physical well-being instead solely on weight, or some such line of thinking.
I agree with you and think is more of a practical feature. Samsung devices can not measure weight, though there are some third-party devices for measuring weight that work with Samsung Health . Samsung watches measure body composition with 'weight', which is supplied by the user, as part of the computation.
