Marking or dividing unread messages in subscribed threads

When you check subscribed threads and click on (bold) updated thread you land on that thread you follow.
It was seen on other forum that older messages and new (unread) messages were divided by line, so you can continue reading.

Something like index paper you put into book to know where you ended reading.
(don't know about technical possibilities or if necessary as this forum may have shorter threads)

Something similar is already implemented here. When you've unread posts in a thread, you will see "View First Unread" in the top bar above the first post. Click it and it will jump to the first new message since your last visit.

Thanks, that will help me from now on.