How to add custom fields for classification in Zotero?

Adding custom fields for classification in Zotero is feasible and requires utilizing specific features or add-ons, as core Zotero item metadata does not natively support arbitrary custom fields for direct categorization alongside standard fields like Title or Author. Zotero handles categorization primarily through built-in fields (Tags, Collections), the 'Extra' field for miscellaneous key-value pairs, or Notes. Directly adding custom fields necessitates modifying configuration settings via the Advanced Config Editor (risky for casual users) or employing the third-party 'Custom Field' add-on, which provides a safer interface for defining and managing user-defined fields. Precautions include testing configurations in a new profile first, potential conflicts with future Zotero updates, and ensuring defined fields serve a clear categorization purpose complementing existing metadata. To implement this using the Custom Field add-on: Install the add-on via Zotero's preferences; define new fields by accessing 'Custom Fields' under Tools, specifying field name and type; input values for items via the add-on pane in the item editor. This facilitates custom classification schemes (e.g., project phases, methodological tags) within research projects, significantly enhancing personal data organization and retrieval efficiency for complex research workflows.