Show read/unread status in inbox (all-notifications page)

[cellio]

I received the following request via email:

For notifications > see all, there is no longer any indication of read or unread, nor any way to toggle the same.

Please include this functionality. It makes for easier cleaning of an inbox. It would allow me to open threads in new tabs, and if it's something I can't test at the moment, leave as unread or toggle back to unread (depending on what the default behavior is on open (I seem to have experienced both)).