I don't know whether I should ask here for an issue related to translation. I have a custom selection field, I should add the option from the custom field and the customer selects from the dropdown. I assume when the customer selects from the dropdown and it is not necessary to select again from another language, how can I set the custom field from Toolset?
Once the customer has selected the field in 1 language and that post was then translated in another language then the selected option will be translated to that language as well.
There is no need for the customer to go in and to re-select their select field option.
Does a translation exist for this customer field ? If not then the field can be translated using the WPML string translations plugin.
Once the field is successfully translated then the corresponding option in the other language will be selected automatically.
Please let me know if this clears up the issue for you.
Traditional Chinese is the default language in my site, when I add the custom field and option, it looks the title/value are added as English but not Traditional Chinese. Is it must have the English to the site? I will another site with only one language but not English, how can I ensure the title/value I added from Toolset custom field are for non-English language?
Given that you've set your site's language for Chinese then the text in the custom field should be Chinese when you view the site in its default language.
Only when translating the site to English you should get the English term.
Is it must have the English to the site? I will another site with only one language but not English
No its not a must that you have the English site. I believe you are able to click on the "Add/Remove Language" button to remove the English information on the site.
Regarding further information on translation issues and more advanced assistance I would recommend that you get in touch with the WPML support team, as they are better trained to handle the WPML issue.
They should be able to give you more specific information on this.