Hi @saidtig,
Welcome to the 
community support forums !!
Well, I am not yet expert with Elasticsearch datasource but I think I might be able to help you with what you looking for with Transformation.
Yes, you can use the “filter by value” but then use regex.
Here is a good link to a post which explains as how to use it and also link to the documentation as how to use regex.
I hope this helps.