I reported this on with Bug Report Wizard because it is happening to me too. I'm sure its an bug because its only doing it in opera.

I'm trying to add the new end screen feature that youtube added to the video
editor, I can add elements but I just cannot resize them or move them, only
thing that I can do is click on it and it will open an link just like
annotations do.

Steps to reproduce:

1. Go to your youtube dashboard
2. Press edit on any of your videos
3. Go to end screen & annotations
4. Add an element in end screen tab and try to move or resize it

Actual result:
It doesn't show the resizing frame and I cannot move the elements, It just opens the link to the video or the channel when you click it.

Expected result:
It should show the resizing frame so I can resize the element and when I
hold left click on an element and than move the mouse it should move the
element.

OS: Windows 10 64-bit
URL: https://www.youtube.com
Version of Opera: 41.0.2353.46