This is a separate issue, the other thread is about losing the EditableRange elements when converting to .htm, this is about Aspose not allowing us to insert Bookmarks and EditableRanges (it happens with both classes) inside other elements than Paragraphs.
It is not possible to provide documents as we get an exception when inserting any of those 2 nodes into any other composite node that is not a Paragraph. A code example could be:
node.AppendChild(new BookmarkStart(doc, “My bookmark”));
Given that node is not a Paragraph node, it will throw an exception.
There is a note in the remarks section in the Aspose API in both classes warning about this, but Word does allow them to be anywhere in the document and we need the same behaviour than in Word.