I really liked the old way to use sidebar (hide but still be able to use on speed dial) and I hope they fix this soon. But in order to keep using Opera, I had to improvise. So, I created bookmarks for every shortcut I use in the sidebar:

Bookmarks > opera://bookmarks/
Downloads > opera://downloads/
Extensions > opera://extensions/
History > opera://history/
News > opera://news/
And a few others...

Every bookmark has it's own icon and you can put it on speed dial.

Bookmarks:

Speed Dial:

I hope I have helped someone.