When I unfold too many nodes, and the node position is too close to the right sidebar, so it has not enough room, instead of the scrollbar to get smaller (so I can scroll to the right to see the whole line), firebug breaks the line. How can I disable this behaviour? On chrome I have the option to disable line breaking (word-wrap).
Note: I’m not sure if this question is for Stackoverflow, so I suppose it can be moved to the appropriate site by a moderator.

You should have better asked inside the Firebug discussion group. That’s normally the only place were the Firebug developers (like me) are answering questions.
Unfortunately there’s currently no such option within Firebug.
You can either