Try open inspector on it (by halo menu alt+shift+click on Mac). And then you can evaluate:

self delete.

or��

World removeMorph: self

2017-02-22 14:12 GMT+01:00 Raffaello Giulietti <raffaello.giulietti@lifeware.ch>:
Hi,

after 3 minutes working, I'm in a situation where a System Browser window cannot be closed. While the button is there, with tool tip and visual feedback, clicking it simply does nothing. Minimization and maximization still work.

Is there a way to force a close?