The video showed up a bug in the client, where you can't add a lot of plugins at once, if the combined path names exceed 255 characters. This bug is fixed in version 4.45.
Meanwhile, you can speed up adding multiple plugins by shift-clicking the file names to add half first (eg. four or five of them), and then clicking "Add" again, and shift-clicking to add the remaining ones.
So you should only have to click Add twice, rather than 11 times as I did in the video.