You can click on a heading that includes a number of subforums and search that group of subforums with one command.
Does that help?
For example, clicking on Hogan's Alley will bring up this page:
It's a listing of only the subforums that make up Hogan's Alley.
Now clicking on the "Search this Forum" tab on the upper right hand side of the listing allows you to search only the subforums displayed in the listing.
You can click on "Search this Forum" and select Advanced Search.
Then you can select...
Find Posts from
"Your Last Visit"
..and search using 'the' as a search term.
That will bring up all the new posts from all of the Hogans Alley subforums since your last visit.