I'm not sure if it's even possible with how Windows handles the Windows Key, but there are a bunch of things that Windows just handles better but I also want the same convenience of opening it using the same button.
I would advise you to look into something like AutoHotkey. With that you can bind double Windows key to whatever shortcut you set EverythingToolbar to trigger on. By default this is Win+Alt+S.
I'm not sure if it's even possible with how Windows handles the Windows Key, but there are a bunch of things that Windows just handles better but I also want the same convenience of opening it using the same button.