Hi Sean, thanks very much for your feedback and feature request. We use Filing Assistant internally every day too.
You should be able to achieve a similar outcome by using the Edit Folder feature, which can be accessed via the left hand side menu or by double clicking on the folder’s description column (see link below).
In the Description: field, you can add any keyword you like, either from the right hand side Keywords list extracted from the email or simply just type the keyword manually in the correct format, such as [web]. Filing Assistant will use these keywords to give the associated folder a higher ranking when it is matched with an email’s address/subject data or when you type text manually in the search field.
I hope this will assist you to customize Filing Assistant to better meet your needs.
Please let us know if you have any questions.