gtk:window-unminimize (window)

window -- a gtk:window widget

Asks to unminimize the window. Note that you should not assume the window is definitely unminimized afterward, because the windowing system might not support this functionality. Other entities, for example, the user or the window manager could minimize it again, or there may not be a window manager in which case minimization is not possible.

You can track the result of this operation via the state property.