I created another small plugin to extend the NetBeans IDE with RFE #190839 and #221151. I know this type of plugin already existed in the past, but the old one (https://blogs.oracle.com/gridbag/entry/netbeans_module_close_other_projects) was unmaintained and unavailable for newer versions of NetBeans IDE.
Get it from http://plugins.netbeans.org/plugin/45122/?show=true.
In a few days it will also be available the at NetBeans IDE Update Center and you can install it from within your IDE. Stay tuned.