We tipped a little more last cruise we were on (hubby and I), but only to certain individuals.
The bartender: We found a great one, knew when he would be at the bar, and we stuck with him lol. He was great, made really great conversation, told us about his family, and we related on different subjects. Plus, he took care of us as customers so we tipped him extra. He helped make our cruise that much more enjoyable.
The Room Attendant: He went above and beyond in getting certain things for us and telling us great places to visit while in port. His attention to detail was great and he never missed a beat. We tipped him an extra $50.
The Waitress: We had MTD but was able to have the same waitress every night. She was amazing, professional, and took great care of us as customers. I felt she went above and beyond with certain dietary requests and such, so we tipped her extra as well.
We kept the "mandatory" tips, but when we tipped extra, we gave them all cash in envelopes. I'm not sure if the "mandatory" tip goes straight to them or not or how it's split, etc, but since I felt that their service went above and beyond for us, I wanted to make sure the cash went straight to them.
However, don't feel compelled to tip extra just because. Like someone else stated, the tip that is already set works out for them as well, because you have to remember, you aren't the only ones tipping them. I will tip more when I feel the service warrants it, and in that particular case, it did. Mind you, the last time I cruised was pre-covid, so protocol may have changed since then.