A DDG search finds https://www.makeuseof.com/how-to-keep-hands-warm-typing/ with suggestions:

1. raise the temperature (if possible)

2. Use Pomodoro to Move Around

3. Wear Typing Gloves (or fingerless gloves)

4. Make a Tent

5. Add Candles

6. Drink a Warm Beverage

7. Use Dictation and Voice Control

https://officetopics.com/how-keep-hands-and-feet-warm-at-wor... suggests:

1. Wear something warm

2. Keep your head warm

3. Drink something warm

4. Move to a warmer corner of the office

5. Walk when you take breaks

6. Make sure to stretch

7. Get an electric heating seat

8. Use a small heater

That seems to cover the large majority of suggestions people have.

https://www.reddit.com/r/learnprogramming/comments/1o58q1 has people suggesting chemical hand warmers, or electically (often USB) heated gloves, but more as a thought than a practice they actually do. Also, one pointed to arthritis gloves, at https://www.transcriptiongear.com/arthritis-gloves-1-pair.ht... , several suggested improving one's physical fitness, and a joker suggested the "reverse turtleneck", at https://i.imgur.com/PCouapP.jpg .