At the top of this page, select New Posts next to the lightning bolt. On that page, above the Gray bar is a text string "Mark Forums Read"
ah see I didn't know it was there because I don't use the "New Posts" page. Never have. I only browsed from the main forum pages. That button should be available on any of the pages, like most forms. However to get to it, it's not the same as you describe. There is no, "Lightning Bolt." I had to select the "Forum drop-down menu" at the top of the page. Are you viewing this forum on mobile or something? Well thanks... anyway. ^.^
