Thanks for replying. I found a work around and now my specific setup with NoMachine is usable.
It seems that NoMachine Player controls Server mouse and keyboard only when its window currently have focus. If I make the Player window lose focus of a Server shared screen, e.g by clicking on another window and then moving my mouse to the Server (using Barrier) than everything works as expected.
I want to propose a small feature/option to have a Setting in Keyboard and Mouse section called something likeĀ “Lose Focus on Mouse Out”. When its checked, Player window should automatically lose focus when mouse leaves the window and on mouse enter, it’ll be focus as it is now.
Best.