Simple answer: Yes.
Need a bit more?
Open "Streaming > YouTube". It may tell you it is redirecting you.
Search for a video you want to save and add to the library.
Click on the video thumbnail. If you don't get a popup dialogue, and it looks like it is going to play the video, but doesn't, Ctrl+Click on the black video box. Or just go back to the page of thumbnails, and Ctrl+Click on the video thumbnail. WAIT for a little bit.
The popup dialogue will give you options. Select the Download options, and set the location and name to save to.
Can't find the downloaded video? Look in the "Service & Plug-ins > Downloads" menu in the Tree. You may need to change tags so that it shows up where you want it in MC Views.
You can't sign-in to YouTube at the moment. That stopped working, at least for me. I think it's the same for everyone, because the Chromium browser MC uses no longer supports sign-in, supposedly for security reasons.
Some videos can't be downloaded. That is a YouTube thing.
