I'm afraid that the toolbar is not outside of the scheduler widget. It is rendered within the scheduler wrapper element and it is part of its main content.
The "autogenerated HTML content, which is outside the widget, e.g. detached popups, dropdowns, etc." are exactly what the documentation said - detached elements like popups, dropdowns which are generated by the widget, thus the developer does not have control or knowledge where they are located in order to manually remove them from the DOM tree. For example such autogenerated widgets in the context of Scheduler is the popup events editor, or the toolbar calendar used for navigation.
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