The practical answer
Yes, baggage storage is available at Changi Airport and Jewel. This matters because dragging cabin bags through MRT stations, hawker centres, and crowded attractions is a fast way to ruin a short layover.
Charges apply, so treat storage as a stress-reduction cost rather than a free service.
Jewel and terminal storage
Changi's baggage storage directory lists locations in all terminals and Jewel. Jewel's traveller information also notes Left Baggage at Level 1 so visitors can explore without hand-carry luggage.
Some Jewel attractions do not permit luggage, so do not assume you can bring bags everywhere.
Early check-in alternative
If your airline supports early check-in, dropping your bag before exploring can be better than paid storage.
Always check the participating airline and time window because early check-in varies by airline and departure time.
Next practical step
Plan a luggage-light layover