This is too expensive for most personal users, it may be suitable for commercial organisations and YouTube professionals. (If you put the costs on the description you would avoid getting rated down for that.)
I clicked the toolbar icon while playing a video clip on Twitter, and a YouTube Hindi news broadcast. The icons appeared on the videos correctly. When clicked, a dialog opens requesting Google Cloud Services API key. A link opens instructions how to set up an API key. The instructions did not explain how to restrict the Key (recommended in the Key window), or guarantee any security of the key which you are giving to the Dev.
The Google cloud platform requires credit card details. It costs US$100 per month, after 3 month free trial (not auto-billed, unless you activate it first). 2 APIs are needed, the subtitle generator costs 4.45c per minute after 60 free minutes, but the translator costs $US45 per minute!!!
I did not provide the API key I generated to the Dev, because of security concerns. So I have not tested it.
Dev, could you provide an option to generate subtitles without having to pay for translation? There seem to be free subtitle translation add-ons available (not checked though).

I added a GCP account, but the subtitle window hangs at "Subtitles are being generated...".