Until this functionality is implemented, another possible workaround would be to define a custom field in all items that should be hidden, using a unique name (or value) — preferably something short, like x86. Then you can exclude these records using advanced search expressions, like the following:
>bank* -x86
If it is possible that your obsolescence codeword appears somewhere in a non-obsolete vault entry, then you can restrict the detection of that codeword to only custom fields, as follows:
>bank* -fields:x86