Represents a (natural) grouping of SimDM/InputParameters.
Especially in protocols with large numbers of parameters it may be useful to group these
for browsing purposes for example. As browsing is likely an important mode of access to  SimDM/Resource-s stored in a SimDB for example, this possibility was introduced.
But the main use should be reserved for semantic groupings. For example all parameters together defining the cosmology a certain simulation is run in. Or the parameters setting "merely" numerical properties such as smoothing lengths.