base_question_type

base_question_type specifies settings which are applied to all Question types, unless they are overwritten/extended by question_types or question_type_templates. If you add the base_question_type option shown in the preview, the penalty_score and multiple_responses attributes would be hidden in all Question types. stimulus would not be hidden as it is specified in the shown array as well.
The hidden_sections specify that the more options heading and divider are hidden for all Questions, whereas the more options content is displayed as it is specified in shown_sections.

{
    "base_question_type": {
        "hidden": ["stimulus", "penalty_score", "multiple_responses"],
        "shown": ["stimulus"],
        "hidden_sections": ["more_options.heading", "more_options.divider"],
        "shown_sections": ["more_options.content"]
    }
}

question_types

question_types specify settings which are applied to certain Question types, unless they are overwritten/extended by question_type_templates. The settings in the preview would result in the following: multiple choice Questions would inherit penalty_score and multiple_responses as hidden attributes from base_question_type. This would be extended by stimulus. However, penalty_score would be removed as it is specified in the shown array. The end result would be that stimulus and multiple_responses are hidden for multiple choice Questions.
The hidden_sections array is merged with the array from the base Question type. When not specifying .heading,.content or .divider all these subsections of layout will be hidden. Sincemore_options.divider is specified in shown_sections, the dividing line will be visible.

{
    "base_question_type": {
        "hidden": ["stimulus", "penalty_score", "multiple_responses"],
        "shown": ["stimulus"]
    },
    "question_types": {
        "mcq": {
            "hidden": ["stimulus"],
            "shown": ["penalty_score"],
            "hidden_sections": ["layout"],
            "shown_sections": ["more_options.divider"]
        }
    }
}

question_type_templates

question_type_templates specify variations on base Question types. The settings in the preview would result in the following: MCQ - Base Question would inherit the settings specified in the mcq section of question_types. MCQ - New Template would inherit stimulus and multiple_responses as hidden attributes from question_types. These are extended by penalty_score. stimulus is removed as it is specified in the shown array, resulting in multiple_response andpenalty_score being hidden.
Since more_options.divider is specified in hidden_sections the dividing line will not be shown for MCQ - New Template.

{
    "base_question_type": {
        "hidden": ["stimulus", "penalty_score", "multiple_responses"],
        "shown": ["stimulus"]
    },
    "question_types": {
        "mcq": {
            "hidden": ["stimulus"],
            "shown": ["penalty_score"],
            "hidden_sections": ["layout"],
            "shown_sections": ["more_options.divider"]
        }
    },
    "question_type_templates": {
        "mcq": [
            {
                "name": "MCQ - Base Question",
                "reference": "e58f696f-4c70-4169-83b9-dfdeaa6e5cef"
            },
            {
                "name": "MCQ - New Template",
                "reference": "f171f0dc-5703-41b4-beb1-430bb7bddf45",
                "hidden": ["penalty_score"],
                "shown": ["stimulus"],
                "hidden_sections": ["more_options.divider"]
            }
        ]
    }
}

Customizing Question Attributes and Templates using the Author Site

If you need to use custom Templates in the Author Site, you can open a request with the Support Team and provide the JSON for us to add to your Author Site.
If you need to add any custom styling, you can create a single CSS file for use by your entire consumer.

The file must be hosted on a secure server (the URL must use HTTPS) and you add the URL via the self-management tool, Learnosity Console. A Console admin can find the value under: Expand Menu > Configuration > Consumers > [select any/each consumer to edit, one at a time] > API Options.