Wordzilla lets you upload your existing translation files, see all your strings in one place across languages, and auto-translate missing entries using OpenAI.
Supports JSON, XLIFF 1.2/2.0, CSV, and Excel. You can export back to the same format you uploaded.
The editor is completely free, you can give it a try. New accounts also get 100 free credits to test the auto-translation (costs roughly 0.015 credits per character, so a typical small app runs a few dollars).
Any feedback is greatly appreciated.