My company recently switched to Cloud Jira. When I'm looking at an individual ticket, the center and right columns, the actual ticket and the details information panel on the right, don't auto-expand to full width of the browser window. I've got a 21:9 ultra-wide monitor, so sometimes my browser windows are rather wide. With some tickets that have some particularly large amounts of text in the description or comments, I'll go full monitor width to display it more all at once.
However, in this newer version of Jira, I can't do it. Or at least, I can't find an obvious toggle to allow auto-reflow to expand width of the columns to match width of the browser window.
