Currently, visiting a topic page will mark it as read.
As an editor, I might read the topic, and decide halfway through that I don't have time to reply at the moment.
I want a way to mark a topic as "unread", so that it's back to being highlighted in my Notifications.
This would be similar to the way I will often use "mark as unread" in email/gmail.
This would be similar to the way that an editor can choose to not mark a LQT topic as "read".
Context: This was recently discussed in https://www.mediawiki.org/wiki/Topic:Se14547daaj65kpa where @He7d3r wrote
the "way to mark the ones that I've read" must not be automatically marking them as read as soon as I open them, because sometimes I can get an idea that the message is complicated to deal with even before finishing reading it... and I would want to mark it as unread, for resolving the issue later.