Regarding your case, unfortunately, what you are looking for is not supported.
Based on the way this integration works, webhooks are getting triggered only when a language of a resource is fully translated or reviewed.
Please also note that webhooks are not being triggered when an already 100% translated target language is edited/updated. This is an expected behavior based on the current implementation. So, if you want to re-trigger the webhook you need to unreview or remove the translation from an already translated string and retranslate it so that the language will reach 100% again.
Another suggestion I can provide you with is to:
#1 : Create automated tasks that will pull the translations via API/Client once per day so as to ensure that you have also the recently modified translations.
#2 : Get resources’ statistics via API as it is described here and decide based on a certain translation completion (100%, 80% etc…) if the translations files should be pulled or not.
We appreciate your feedback and thank you for sharing your concerns with us. I will definitely pass your feedback along.