If I select an instance in the Instances tab, and run Show Nearest GC Root on it, and then want to file a bug report about the reference chain, there is no easy way to do that. There is no (apparent) UI gesture to copy the reference chain as text (e.g. in NbTestCase.assertGC format). File > Print is disabled.
Cumbersome workarounds: type in the details in a bug reporter manually; use a desktop screenshot utility and cropping the image to the area of interest.
Bug #201251 is similar.
I notice that Ctrl-C on a line in the reference graph does copy that line to the clipboard, e.g.
controller org.netbeans.core.output2.Controller class Controller
which might be a feature of the tree table view; in any event, (1) "Copy" is not exposed in the context menu, (2) there is way to multiselect lines so you would need to do this repeatedly.
Integrated into 'main-golden'
User: Jesse Glick <email@example.com>
Log: #205250: UI to copy nearest GC root trace to clipboard
Copying automatically when action to show root reference is run.
Very convenient, though not necessarily discoverable.