I would like to see NIK plug-ins to also be available as standalone apps. Thus one is not always tied into using Ps, Lr or ON1 to get to NIK.
It is already possible. Just navigate to the NIK install directory where you see all the exe files. Drop a sample image on an exe using drag drop. This also works with shortcuts to the exe files on the desktop.
Yes, that is already possible and @Asser explained you one of the ways. But to make it more convenient there is a request NIK Collection Add Start Menu shortcuts/icons for standalone applications for which you can vote.