Apparently the people who develop Vivaldi believe that adding a screen capture feature to the browser is a good use of their time. Perhaps if you don’t use any other web browsers, and you only ever need to capture screenshots of web sites, and never of anything outside the browser, this would be a useful feature. The rest of us will use the much more powerful features of general-purpose screen capture tools like ShareX.
Aside from the arguably pointless addition of screen capture, Vivaldi 1.7 further improves audio handling, and includes tweaks for domain expansion in the address bar. More importantly, Vivaldi now warns users when they navigate to a non-encrypted page that prompts for a password.
You can see the complete list of changes for Vivaldi 1.7 in the official release announcement.