Please reference to original ticket SUPPORT-8744 for more information.
For short 'Multivalue composite language dependent fields are not displayed when we "add" a new one in a different language than the default'. Reproduce steps:

1. Use attached dialog configuration to have configured i18n supported multivalue composite field.
2. Open the dialog, switch to DE for instance
3. Click ADD button to add a new configured field, put some values into it
4. Switch back to EN to see your added field disappear
5. Click SAVE button then reopen your dialog to see the empty field appear in English (since it has no content in English but in DE)

Expected result:
Allow switching back and forth on i18n multivalue composite field and save it properly.