I cannot use the design studio totally

[hdugzx]

I've closed the windows of it,below is what it looks like

I cannot restore default settings.

[jsulm]

@hdugzx I never used Design Studio, but there should be a menu like "View" or "Windows". Look in "..." in the top-right corner. You also can check the settings. In QtCreator you can disable/enable menu by pressing Ctrl-Alt-m - maybe it also works in Design Studio.