There should be an option to search through ISO or FT topics, specifically in Diablo 2 trading. It's horrible searching for people looking to buy specific items when you have to scroll through gigantic FT lists because they include the keyword(s) you entered.

Do you mean a search function for specific topics or a search function to sort FT from ISO and vice versa, to separate your searches?

As long as you have either FT or ISO opened it should only search for those topics. If you have "All" opened, it will search for every kind of sale.

The feature to do separate searches was already added in this topic a few years back: Add Iso/ft Option To Search Function!

Also remember to add a poll in your site suggestions, otherwise they will get closed. You can check this: How To Post A Site Suggestion.