I've noticed on the new web forum that the "notifications button/bell icon", you can select "Mark All Read" (the Checkbox icon). However, I don't see any indication that this does anything. Expected behavior would be that everything displayed in the pulldown would then disappear. However, it continues to show threads that I read days ago and marked as such with this button.
Perhaps it's broken, or I am expecting the wrong result? Currently, I don't see a method of "just show me threads/posts that I haven't already read.
This is one of the difficulties with web-based forums. Once threads get long with inter-nested replies, they become very unwieldy to quickly navigate.
Another item: It seems as though replies to posts in the threads do not always appear below the post to which you have replied. This may be related to this forum software--I don't recall this ever being an issue in the original Legend Forum app.