Creating a Control Set.
if you select a number of related controls and right click on those controls, you get an option to save a Control Set.
Once clicking on "Save as control set..." you are prompted for a Control Set name. Spaces seem to work.
Using the Control Set
Voltage Modular designer will then show the newly saved Control Set in the Controls menu under the "Control Sets" group.
These Control Sets can now be dragged onto future module designs. Makes reuse a breeze.
The sets seem to be marked as "Linked" (another right click option on the design tab for the controls) that allow you to drag the controls as a group. These can also be "Unlink"ed.
You can also drag multiple of the same control set onto the designer without an issue.
Renaming/Deleting a Control Set from the control menu
Right-clicking a specific Control Set in the Control menu gives you the option to rename or deleting the Control Set.
VMD did seem to get a little confused when I created/deleted the same Control Set multiple times while testing the feature, but restarting VMD fixed the issue.
Locating the control set files
To ensure you can back these up (e.g. for source control), on Windows, Control Sets are stored under the Documents\Voltage Module Designer\control sets\ folder with a ".ctrlSet" extension.
I found that deleting a file in this folder also removed the control set from the VMD app when it was restarted.