Problem: The client is using ACF with an additional plugin called ACF Custom Database Tables to store ACF field values in separate tables, which WPML does not automatically recognize. The client needs to know which WPML hooks or filters to use to integrate these custom tables with WPML's Advanced Translation Editor and how to handle incoming translations for storage in these custom tables. Solution: Unfortunately, WPML does not provide specific hooks for integrating custom database tables used by ACF Custom Database Tables. We recommend scanning ACF and its addons for new strings at WPML > Theme & Plugin Localization and then translating these strings at WPML > String Translation. If the fields are added to the wp_options table, they can be translated using WPML String Translation, as detailed here: https://wpml.org/documentation/support/language-configuration-files/translate-strings-in-wp-options-table/. For further customization, additional development and compatibility coding might be necessary.
If this solution does not fully address your issue or seems outdated, we highly recommend checking related known issues at https://wpml.org/known-issues/, verifying the version of the permanent fix, and confirming that you have installed the latest versions of themes and plugins. If further assistance is needed, please open a new support ticket at WPML support forum.