Something similar to defining several conditions for Custom Search in query.cgi would be great (like an "Add another condition" button?), as I'd like to have a specific custom field only displayed in case of either component == foo or component == bar. Going for two custom fields with the same function to work around sounds really cumbersome (e.g. for querying or administrating I'd always need to cover both).

This feature already exists in Bugzilla 4.2.