Current versions of gnome’s “Keyboard shortcuts” control panel applet don’t have an entry for “System->Show the activities overview“, so you can’t edit it.  Instead, it’s hard coded to the winkey, and  Alt-F1.  No. Bad gnome.  Don’t do that. I want to use that, (in my case, in IntelliJ)

What to do?

gsettings to the rescue.

$ gsettings get org.gnome.desktop.wm.keybindings panel-main-menu
['<Super>s', '<Alt>F1']
$ gsettings set org.gnome.desktop.wm.keybindings panel-main-menu "['<Super>s']"

Presto.