When I'm working on my laptop on the fly the screen is too small, thus I use virtual desktops to increase the available space.
When I'm working on my laptop at home I have a secondary screen. Now I have enough space by default and i dislike the virtual desktop functionality.

Now I asked myself if there is the possibility of using the virtual desktops when travelling and deactivate the feature when I attach my secondary desktop.

Do you know any trick how to do this?

Well, first thing that comes to mind is to just stick to one virtual desktop while you have the two displays (just because you have more than one doesn't mean you have to use them).
Of course in this case you'd probably want it to move all of the windows from the other VDs to the second monitor and back. I believe there should be a way you can trigger an action (like a script or something) when attaching or detaching a display, and then you use that to move the windows around as necessary.