I am having the same issue on latest Opera version 60.0.3255.59. It is quite annoying this issue.
Was it opened an issue? Can we know its number?

Hi,

I've just updated from v. 55.0.2994.61 to 55.0.2994.56, and menu View -> "Show Toolbar in Full Screen Mode" is enabled again and it works.
But I can be sure this is because the update required restart or the issue have been fixed (hopefully for good).

Hi,

I did recently face the same issue.
Opera is quite unstable (v. 48 on High Sierra 10.13)
I cannot add a bookmark or create a folder in the bookmarks bar. It crashes every time.
Moreover, when Opera is in the fullscreen mode I cannot create a new (private) window.
In the previous version I could not use the trackpad gestures to zoom in or out.

It became so buggy, and some issue affects basics functionality of the opera and are critical (crashes) that I started to doubt about their functional tests suite.
I really like Opera browser, but for me performance and stability of the product is very important, so I thing I will be going back using chrome.

jtonic