How about ‘New posts’ and ‘Unread Posts’ buttons. The rate at which both new stuff columns cycle through means that it’s difficult (for me) to keep track; a new topic can arrive, not get replied to and disappear within 24 hours. So unless one surveys the entire site, one wouldn’t know it existed.
'The time has come" The walrus said. "To talk of many things: Of shoes--and ships--and sealing-wax--Of cabbages--and kings--And why the sea is boiling hot--And whether pigs have wings."
The software does not have that functionality, sorry.
However, you can subscribe to forums not just topics.
So if you like say WWII, subscribe to the WWII forum and you will get a single e-mail that notifies you of each new topic posted in WWII.
If one of those topics is of interest, then subscribe to the topic and get a notification via e-mail of new replies for that topic.