@leocg Interesting. I've tried that already without any results, but now it worked.

Much appreciated.

So, In order version of the Opera GX, the sidebar messenger was alright, but in the new one it was changed.

This is the contact list (censored obviously):

When I enter the chat with someone, in order to change the chat, I have to click on the circled arrow.

It's a minor thing, but the older version allowed me to switch to an another chat directly, instead of going back first, meaning that extra click is needed. It's a minor thing, but it is annoying since I got used to a previous system which was better. I don't understand why it was changed.