Thread:Extension talk:CategoryTree/Combine categories by logical operators?

This might be in fact an enhancement request...

Is it possible to show one tree of pages which below to category a and b only?

Use case: Our wiki contains product information. So every article belonging to product gets the product name as category. When an article is a FAQ, it gets the FAQ category as well (now we can see e.g. all FAQs regardless of the product). Goal would now be to get a FAQ list for a certain product as well without needing to create another category.

Thanks for every input! backarc