For the bookmarks by the side you can use this extension https://addons.opera.com/en/extensions/details/bookmarks-by-the-side/?display=en

It's more or less what you are looking for.

I don't want to turn off the extensions bar, I like his functionality. But having a main sidebar, it has no sense to have a separate extension sidebar

+1 Opera really need something like this.

I think you already can do it, if you install any "Chrome new tab extension" like zest.is using the Download Chrome Extension. Then you just add the extension link using the Custom New Tab Extensions and voilà! That's what I do to use Toby on Opera ^^.

For the bookmarks by the side you can use this extension https://addons.opera.com/en/extensions/details/bookmarks-by-the-side/?display=en

It's more or less what you are looking for.

I've started using Opera since a long time and I'm delighted with the IM features on the new side bar. But i don't understand why the extension sidebar is still alive. It is so redundant to have two sidebars which do more or less the same things...

What I'm suggesting is that you should consider integrating the extension sidebar into the main sidebar. It would be nice.