By default, whenever you insert a section, it will include an empty subsection by default. If you do not need a subsection, as the section hasn’t been sub-divided, you will need to promote the subsection into section content.
Don’t try to achieve the same result by deleting the subsection number or the num element as that may cause problems with the presentation of the section or for users of the legislative data in future.
How to convert a section with a single subsection into an undivided section
With your cursor in the subsection, right-click and select Promote Element...
How to change the stage of amendments
The promote action will only work if there is one subsection in your section
If you change your mind and want to sub-divide your section into subsections, click Enter to bring up the insert menu and select Subsection (1) which will insert a subsection after your section content, and at the same time convert your section content into a subsection.