I see that after a year there is no progress on this.
I don't understand why this problem is no addressed, this stop me from using this extension and come back to the desktop application

@leocg
This is Opera notification
This is Chrome extension notification

So there is no change in desktop notification opera for me is working like show preview is disabled

@leocg what is this standard you're talking about?
I see that every browser or desktop notification has content and even the chrome extension that uses the same engine (webogram) shows a preview.
The fact that you can choose in the settings to choose an overview of the message (same settings of the chrome extension) indicates that is a bug.

I will like more the Opera extension because it is integrated in the Opera panel (the chrome extension will load as a separate process, that make it less appealing than the desktop version) and I don't think I'm the only one, so I think that very few have this problem

I see that after a year there is no progress on this.
I don't understand why this problem is no addressed, this stop me from using this extension and come back to the desktop application

I agree with the criticality of the function, the new Opera without basic functionalities is far inferior in usability in comparison to other browsers.
I still use Opera only because I use Opera 12 alongside the new Opera, otherwise I had left like many other old Opera users.