This information applies to versions: 3, 4, 5, 6, 7
To restore the Nik Collection Palette (formerly known as Nik Selective Tool) after reducing it to its list of icons, please click on the ":" symbol on the top bar of the window.
Nik Collection 8 introduced the Nik Collection Panel, which is seamlessly integrated into Adobe Photoshop and fully customizable. It replaces the Nik Collection Palette.