Oh, manage to find the nodegraph window at last. It was open all the time and was hiding above the window. That's why clicking the tabs doesnt work - it's already open

Case closed.

I once managed to get the Nodegraph window to appear outside of the screen resolution I was working in.

That had the effect of appearing not to function.

Thanks for replying.

Most probably that's the problem, maybe I 'over-drag' it far too out. Anyway, what did you do to get it working again ...

I've been using the nodegraph editor without any problems till now, but looks like it's not functioning lately. Tried both in the viewport and under the material tab - clicking any of them wont bring out the nodegraph editor window as usual. Did I accidentally clicked anything that deactivates this ...