The issue has been closed
In all PRs, in the Files changed tab, we have Viewed checkboxes. It would be very helpful to have a button above all these or somewhere to click and uncheck all files' viewed checkbox.
It helps a lot in PRs where the files are a lot, (more than 100), and he PR still going. I often go in my PRs and check viewed in the files that are finished, and keep the rest open, while the PR is not finalized.
Unchecking viewed means that your previous "view" should be discarded. If your workflow is that, why check viewed in the first place?
I think your intention is to just see the all files at once, even if you already viewed them. In that case, you should use the toggle button on the very left, not viewed.
Also, using alt+click on that button will toggle all the files open or closed.
<img width="241" alt="" src="https://user-images.githubusercontent.com/1402241/76087528-65d7e600-5fc7-11ea-9a92-66aeaa3b5163.png">
posted by fregante about 5 years ago 
my workflow is actually about unchecking viewed, but thank you for marking as duplicate, I failed to find it before making the issue.
IssueHunt