Thanks for the feature request! I can understand why that might be useful to you.
It sounds like it's related to this feature request: http://talk.dynalist.io/t/option-to-exclude-document-from-global-search/544 (Not necessarily a dupe)
If it's possible, we like to make it explicit that you're excluding a document, so that you don't panic or confused when you forget that you've excluded a document (sounds funny but it will happen). So the search results would indicate somewhere that X number of results are excludes and are viewable if requested.
To anyone reading this: please like or comment if you're interested in this too! That's the only way we can know if more users are interested in this