Survey existing data conventions for method parameters, especially parameter objects

We should survey the way we actually record parameter object data and establish a guideline.

Background

We have a guideline for creating subfeatures for methods' parameters and parameters that are objects. In some cases we follow this guideline (flattening parameter objects), but in many other cases we do not.

Task

Read the existing guideline. Go through the api tree, looking for parameter entries (typically, keys with _parameter in the key name). For each one, record whether the parameter is a dictionary or not, and what, if any, subfeatures or sibling features are associated with that parameter. When that's done, summarize the results: identify the naming and structuring schemes that exist and which ones are most commonly used.

Start with docs/data-guidelines, especially the parameters-and-parameter-object-features section, then search the api tree for keys containing _parameter. Record whether each parameter is a dictionary and its subfeatures or sibling features. Summarize the naming and structure patterns found, noting which are most common; completion is the survey and guideline-oriented summary.