Closed state + Show / Hide Closed issue button
Description
You should be able to toggle the visibility of closed issues on the the issue board and their state of closed / open should be very obvious.
Proposal
Add tabs to filter through open/closed/all issues.
Include a red dot to indicate closed issues:
Original Proposal
Add a button / checkbox to toggle the visibility of closed issues make it obvious which issues are closed or not, when they are shown.