I would like the ability to export libraries into a .csv file
Still not added three years later.
You can now download your full media library to a .csv file.
1) Make sure you have either the "Global Accessibility" or the "Media & Playlists Accessibility Override" settings enabled. You can do this under Settings -> Accessibility Settings.
2) Click on "Media & Playlists" from the left hand menu. Click on "Export Library To .csv" in the table header.
The "Export" option is not visible.
Please note the export option is only available while viewing all of your media, as it exports your complete library. In the screenshot you provided, you were viewing a specific playlist, rather than all of your media.
At this time, exporting a specific playlist is not available. However, that feature will be added soon.