You will only be able to tell a cabin bag weighs over 10kg when the passenger tries to place it in the overhead locker.
Thats when they ask the CC to put it in the overhead locker for them " because it is too heavy for me to lift ".
My answer to that is " Oh well if its too heavy for you then it must be too heavy for me as well ". Any bag that requires two CC to place in an overhead locker is too heavy and should be offloaded to be placed in the hold.
So CC will be expected to risk an injury putting heavier bags in lockers just so pax can save $10 ? WTF