SDK API to access tag element data items?

I'm working on a new feature in an Acrobat Plugin to help with Accessibility programming.

I need a way to access a tag's "Tag Elements" – this is the encoded data pairs that can be seen by right-selecting a tag, selecting "Properties...", and then clicking on the "Edit tag" button. See the attached screenshot for reference.

Essentially, I need to extract the "/Headers" array, or any item value pair (i.e. <"/S", "/TD">).  I've tried PDSElementGetAttrObj, and a few similar methods, but they don't seem to provide the right (or any) data.

I've looked through the SDK API docs and cannot find a function that provides read/write access to this level of data. Anyone have any ideas?