Office Addin Custom Attributes on Range Text - vsto

Question

I would like to know if it's possible to add additional attributes to simple Range text or Paragraph text from my Word Add-in. For simplicity see code below where I can populate the document with text but additionally i would like to store additional but behind the scenes info along with that text. Ultimately I want these read these custom attributes using the Open Xml SDK when these documents go through a processing stage.
private void AddAttributedContent(string documentContent)
{
var doc = Globals.Factory.GetVstoObject(Globals.ThisAddIn.Application.ActiveDocument);
var range = doc.Range();
range.Font.Size = 12;
range.Font.Name = "Calibri";
range.Underline = Word.WdUnderline.wdUnderlineSingle;
range.Text = documentContent;
// range.AddOpenXmlProperty("MyProp", "MyValue");
var para = doc.Paragraphs.Add();
para.Range.Text = documentContent;
//para.AddCustomProperty("MyProp", "MyVal");
}
Edit:
Ideally our property would sit inside of the resulting RunProprties :

Answer 1

No, you can't do that. You could probably do it with a content control or a text box though.
For a ContentControl, you could probably use Tag (if this is like sources, it probably has to be unique, though the description seems to imply it's meant for the purpose you need) or Title.
The Tag property is different from the Title property in that a tag is never displayed while a user edits a document. Instead, developers can use it to store a value for programmatic manipulation while the document is opened.
For a text box (a Shape), you could use AlternativeText or Title.
Note that altering Title (in both cases) or AlternativeText will probably affect the way the document is displayed if you save it as HTML.