You’ll be left with NetBeans having opened/selected your new Project Group, which should be empty. Now just close NetBeans.
The next step is going to assume that you are on a Microsoft Windows platform.
Right-click the NetBeans program icon on your Desktop and select Properties in the popup context menu.
Now just append the text --open-group Startup to the Target text box.
Now just click the OK button to save.
Having made these changes, whenever you launch NetBeans (via your Desktop shortcut) the IDE will open up your Startup Project Group. Being that this group is empty, the startup times will be much quicker.
What If I’m Not Using Windows?
If you are using Linux or Mac, you just need to alter the way you launch NetBeans. In all of those environments, the NetBeans executable should accept the command line argument to specify the “open group”. If you are reading this post, then I’ll assume you are a developer and can manage to figure out how to do that.