Beeing in the "feeds panel", I kindly assume, that Shift+Up/Down should select block of feeds for any next operation (for example to mark Read/Unread). It works as assumed and probably also as designed.

Unfortunately, the Ctrl+Up/Down has the same  fucntionality, which does not follow the de facto standard for this shortcut (minimally under MS Windows) ... please see Explorer, MS Office, Libre Office, 3rd parties' email clients, etc.

David