How to create multi-reference groups in EndNote?

Multi-reference groups in EndNote allow a single reference to belong simultaneously to multiple custom categories within a library, overcoming the default one-group limitation. This feature facilitates flexible organization of literature based on diverse research themes or projects. Creation requires utilizing Smart Groups defined by specific search criteria or manually assigning individual references to multiple Groups (exclusive to My Groups). Cloud storage is necessary for Groups functionality; sync ensures changes propagate across devices. Critically, groups operate within a single EndNote library and references themselves remain unaltered, only their group associations change. To implement, open the EndNote library and navigate to the Groups pane. Create desired target groups (usually under "My Groups"). Simply select one or more references in your library list and drag them directly onto the names of the relevant destination groups in the Groups pane; alternatively, use the "Add References To..." option after right-clicking selected references. Each dragged reference is then logically linked to all designated groups simultaneously, enabling multi-category classification.