The plugin now stores links to additional categories in a separate table #__wtmulticategories_map and no longer reads them directly from the field values in each frontend query.

The mapping is automatically reassembled when materials and contacts are saved and cleared when they are deleted.

The category lists for com_content and com_contact now work via a map table and subcategories are handled more reliably.

Existing articles and contacts are not automatically reassembled after the update. To fill in the mapping table for previously saved items, use the CLI command, for example: /path/to/php /path/to/joomla/cli/joomla.php wtmulticategories:rebuild-map