This plugin is a simple example of one way to programmatically create grouped devices within an Indigo plugin. The instructions are simple.
After installing and enabling the plugin, create a new plugin device. A dialog box will open requesting a name be set. The name will be used to name all the devices created for that group (additional device groups can be created with new names.)
This example plugin does not include functions to rename existing device groups (but shows one way to ensure names are unique) or any error trapping.