Apparently you really can't rename the actual Toolbox feature as shown here in SW 2016 Help:
Renaming Components in the FeatureManager Design Tree
You can change component file names directly from the FeatureManager design tree.
You can update references to the renamed files in unopened documents at the same time.
Before you begin:
To enable renaming, click.
I dislike the long name of a "CSK for #8 Flat Head Machine Screw (100)1" for example. I would rather have it as CSK #8 FHMS(100)1.
But anyway I renamed this one as a test and then found that when I changed it to a #6 the name stayed the same as #8. I am under the impression that the actual feature name is not being changed. It did however change to a #6 specification in the model.