Is it possible to make it 100% transparent?

I found out how to fix the problem of "scrollbar" at least until they fix the bug.

Instal this extension:

https://addons.opera.com/en/extensions/details/slim-scroll-bar/

Then do a slight modification of that extension making a scrollbar thicker:

https://forums.opera.com/post/81919

It works for me

I downloaded Opera 31.0.1889.131 and now there is not that build any more in the servers of Opera. What happened? Is that build really the "good one", or should I downgrade my browser to Opera 31.0.1889.99?

...and maybe it will be an opportunity for them to improve customizing of OPERA with skins, as it was "19 versions" ago...

"I downloaded the newest Opera for Windows 10 and the scrollbar on any website seems like it is from the 90's, Opera also doesn't display any special characters(ascii I assume), it only displays a white square/rectangle."

I hope Opera Team will fix it soon...