how to add to search fields

Document ID : KB000106778
Last Modified Date : 16/07/2018
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In the advanced search tab, you can click on the magnifying glass to bring up a list of fields to search against.

Can we add our own custom fields to this list? e.g. we add ztest field to all of our forms. We'd like to be able to search for  tickets  using this new custom form field. Possible?
we are not supporting the customization search fields as the data is in the DB as well as in the code. so, its difficult to add as part of a customization and if we add\fix to support it drastically reduces the search performance