Most probably there's no way to do that.
Here's what they say on their site:
TED uses an HLS-based player (as opposed to Flash) that’s built in-house.
The video player is designed to automatically adjust video quality based on your internet bandwidth. If you find that the video quality is poor or that the video pauses too often, try downloading the talk to ...
Since you already know the name of the video you want to download, you can go to the Ted Talks List and download it from there.
You can also use the Ted Talks Downloader to download multiple videos at once.
Actually it is possible by simply adding the string /languagecode/ (e.g. /en/ or /de/).
You just have to check beforehand if the subtitle already exists! The setting you cannot store though is the "interactive transcript". But once the language is set, the transcript—when opened—is set to that same language (i.e. the translation, not English) as well!