I have Opera 62.0.3331.66 on a PC running Windows 10 Home 64 bit and Manjaro (haven't checked the version number installed on the Manjaro drive), and Opera 52.4.2517.140781 on a P20 Pro running Android 22.214.171.1243, and I'm having some trouble syncing my tabs across devices.
For example, if I have 2 windows open with 10 tabs each on my PC, I am able to see all of the tabs on my phone but they are not grouped together by window. Likewise, if I close those 2 windows on the PC and want to re-open them, all I can see is 20 individual tabs in my history. I'm new to Opera, so maybe I'm just not looking in the right place or have my settings configured incorrectly, but I can't seem to figure out how to recover groups of tabs together. It's possible to re-open each tab individually, but I am often working with dozens of tabs simultaneously so I prefer to handle them in groups as I previously did with Chrome.