Answer: Paragraph style copy/renaming

Timothy Rylatt is right, you can refer to his point and implement it, the following code I implemented is a similar one, you can try first:

Sub Paragraph_style_copy_renaming()
    Dim destStyleName, sourceStyleName, d As Word.Document, e, i
    destStyleName = Array("BT Heading 1", "BT Heading 2", "BT Heading 3")
    sourceStyleName = Array(WdBuiltinStyle.wdStyleHeading1,