Add a custom section programatically to a work item in RTC

I have an editor presentation which has custom subsections with custom attributes.

Rather than building the editor presentation with say 5 custom subsections already present when the user may not need all 5, I'd like to allow the user the ability to check a box, press 'Save' and have a plugin check if the box is checked and if so create a new customized subsection programmatically.

I can't find the API to create custom sections programmatically. Does it exist?