Please consider adding a new reference style for translated book or translated journal article. I highly think that this is important. Thank you
The reference types for book, book section and journal already have fields associated with translated author and translated title. – The trick is encorporating these into the templates for those ref types in your chosen output style.
What are you trying to get with which output style?
for example, see the ref type list (bottom part) for book in first attached image, and the use of the translator field in the APA output style in the second image.