Thank you so much for the info. I was trying to learn that but you know what there is nothing shows "edit thread" when I click on top right. There is "share", "bookmark", "#1". That's all, unless I am looking the right place...
This isn't a 2-step process so if #1 doesn't work, simply move on to #2. Part #1 doesn't have to work in order for you to move onto part #2.
Here's another way of illustrating it:
So in your case, all you need to do is click the report button and ask for threads to be marked solved in the future until you find yourself able to do method #1 instead.
Some people on this board will be able to mark their own threads solved whereas others won't. It's to do with the amount of time that has passed since you first created the thread and/or user status like no. of posts/reaction score that determine whether people can or can't do it via method #1.
So if you click the menu highlighted as 1 and you can't see any option to 'edit thread' and change its status - then it means you can only get it changed by following the alternative method which is simply to click report and type a message requesting it to be marked solved.