Insert an Element with all the Required Content

The API ro.sync.ecss.extensions.api.AuthorSchemaManager can propose valid elements which can be inserted at the specific offset. Using the method AuthorSchemaManager.createAuthorDocumentFragment(CIElement) you can convert the proposed elements to document fragments (which have all the required content filled in) which can then be inserted in the document.

AuthorSchemaManager schemaManager = this.authorAccess.getDocumentController().getAuthorSchemaManager();
WhatElementsCanGoHereContext context = schemaManager.createWhatElementsCanGoHereContext(this.authorAccess.getEditorAccess().getCaretOffset());
List<CIElement> possibleElementsAtCaretPosition = schemaManager.whatElementsCanGoHere(context);
loop: for (int i = 0; i < possibleElementsAtCaretPosition.size(); i++) {
  CIElement possibleElement = possibleElementsAtCaretPosition.get(i);
  List<CIAttribute> attrs = possibleElement.getAttributes();
  if(attrs != null) {
    for (int j = 0; j < attrs.size(); j++) {
      CIAttribute ciAttribute = attrs.get(j);
      if (ciAttribute.getName().equals("class")) {
        if (ciAttribute.getDefaultValue() != null
            && ciAttribute.getDefaultValue().contains("  topic/image ")) {
          //Found a CIElement for image
          //Create a fragment for it. The fragment contains all required child elements already built.
          AuthorDocumentFragment frag = schemaManager.createAuthorDocumentFragment(possibleElement);
          //Now set the @href to it.
          //Ask the user and obtain a value for the @href
          //Then:

          String href = "test.png";
          List<AuthorNode> nodes = frag.getContentNodes();
          if(!nodes.isEmpty()) {
            AuthorElement imageEl = (AuthorElement) nodes.get(0);
            imageEl.setAttribute("href", new AttrValue(href));
          }
          //And insert the fragment.
          this.authorAccess.getDocumentController().insertFragment(this.authorAccess.getEditorAccess().getCaretOffset(), frag);
          break loop;
        }
      }
    }
  }
}