gotk4 ApplicationWindow does not show after Hide()

[cvq]

From mainAppWindow:
...
OpenChildAppWindow(app)
mainAppWindow.Hide()
//----------------------------
From OpenchildAppWindow:
childAppWindow := gtk.NewApplicationWindow(app)
.....
childAppWindow.Connect("destroy", func(){
mainAppWindow.Show() // but mainAppWindow does not show
})
//----------------------------
If I use button "destroy" signal, the mainAppWindow shows as expected:
btn.Connect("destroy", func(){
mainAppWindow.Show() // it shows
})
//----------------------------

Please help to fix. Thank you.