Control Center
I accidentally deleted the Cellular Icon in my control center On my Iwatch 5. How do I get it back?
Apple Watch Series 5, watchOS 6
Are you sure that you didn't move it?
I don't think it is possible to add nor remove icons from the control center.
I have tried to delete without success and there is no mention of deleting or adding on the apple help sites.
See https://support.apple.com/en-ca/guide/watch/apd06bc15da1/watchos