Just start typing.

Maybe because you've invoked the Discard with the focus in the Repositories view and not in the Files view? If the focus is in the Repositories view the Files view selection does not matter for any command.

Accidently Discard is prevented by a confirmation dialog.

It is not planned for 18.1, but maybe 18.2.

I thought to have it added where users would search for it.

Currently, views are displayed in tabs. And currently, you can open multiple repositories in the same repository window.

Yes, this could be an option, but IMHO a bad one - tabs inside tabs are considered bad UI design.

BTW, how to handle the case where multiple repositories would be opened?

Do you know any other Git GUI client which already supports bisecting? Until now I only have done manual bisecting with a "good" and "bad" branch.

Sorry, I meant Deactivate. You can find it in the context menu.