Kirby, no, unless you have 2 chorded keyboards that let you type everything with one hand, and you have eyes like a chameleon that can look at 2 separate screens at the same time, or you have someone else working in the same room but logged in as you which isn't allowed by Upwork.
No it's not allowed.
Why would that be allowed?
If you're away from home, and you maid charges you for 3 hours of cleaning and laundry from 9:00 a.m. to 12:00 noon, is it okay if she also charges your next-door neighbor for working those three hours?
Does this not imply that she was not really working fo 3 hours in both places, since she is only one person?