The Upwork team app ( time tracking app) randomly takes six screenshots per hour. All you have to do is open the team app --> login --> select the job --> track time.
To get more information on the Upwork team app please visit https://support.upwork.com/hc/en-us/articles/211064098
Oh, I see. So i guess I cant take screenshot manually. Because sometimes I want to capture my works, send it to my client and put remarks on them. Thanks anyway