Hi Bryan,
I haven't figured out how search filters work and don't know if you can add custom filters. What I do find helps though is in the Introduction section for a guide I add a note like:
''This guide applies to part numbers:''
* ''part1''
* ''part2''
* ''part3''
So that it will show up in search results for any of those numbers as well as confirms to the reader that the guide is applicable to what they are doing. Adding tags for the part numbers is another great method if you want something that is not readily visible but will return in search results.
Hopefully I understood your question correctly and this helps you out.
- Forrest