The ability to create custom parameter groups is already available thru the API. It would be great if it was standard functionality in the parameter window. As you can see by the attached screenshot, Inventor already has some of the tools available to manage these groups. Once I created the groups thru the API, standard Inventor allow you to remove the group. Almost like the feature was started but never complete.
This helps tremendously when making parametric assemblies as well as skeletal modeling and using iLogic. A loop can be used to send all of the parameters of a specified group to a specific part without having to write the sending 1 parameter at a time.