Google Apps Script that will split your Google Doc into separate documents based on Heading 1

function splitDocByHeading() {
  var doc = DocumentApp.getActiveDocument();
  var body = doc.getBody();

  // Create or get the 'Split Documents' folder in your Drive
  var folders = DriveApp.getFoldersByName('Split Documents');
  var folder;
  if (folders.hasNext()) {
    folder = folders.next();
  } else {
    folder = DriveApp.createFolder('Split Documents');
  }

  var numChildren = body.getNumChildren();

  var currentHeadingText = null;
  var elements = [];

  for (var i = 0; i < numChildren; i++) {
    var element = body.getChild(i);
    var elementType = element.getType();

    if (elementType == DocumentApp.ElementType.PARAGRAPH) {
      var paragraph = element.asParagraph();
      var heading = paragraph.getHeading();

      if (heading == DocumentApp.ParagraphHeading.HEADING1) {
        // If we have collected content, create a new document
        if (currentHeadingText != null) {
          createDocument(currentHeadingText, elements, folder);
          elements = [];
        }
        // Start new collection
        currentHeadingText = paragraph.getText();
        elements.push(element);
      } else {
        // Collect elements under the current heading
        if (currentHeadingText != null) {
          elements.push(element);
        }
      }
    } else {
      // Collect other elements (tables, images, etc.)
      if (currentHeadingText != null) {
        elements.push(element);
      }
    }
  }

  // Create document for the last heading
  if (currentHeadingText != null && elements.length > 0) {
    createDocument(currentHeadingText, elements, folder);
  }

  DocumentApp.getUi().alert('Documents created and stored in the "Split Documents" folder.');
}

function createDocument(title, elements, folder) {
  var newDoc = DocumentApp.create(title);
  var newBody = newDoc.getBody();

  for (var i = 0; i < elements.length; i++) {
    var element = elements[i];
    var type = element.getType();

    switch (type) {
      case DocumentApp.ElementType.PARAGRAPH:
        newBody.appendParagraph(element.copy());
        break;
      case DocumentApp.ElementType.TABLE:
        newBody.appendTable(element.copy());
        break;
      case DocumentApp.ElementType.LIST_ITEM:
        newBody.appendListItem(element.copy());
        break;
      case DocumentApp.ElementType.INLINE_IMAGE:
        newBody.appendImage(element.copy());
        break;
      default:
        // Handle other types if necessary
        break;
    }
  }

  // Move the doc to the specified folder
  DriveApp.getFileById(newDoc.getId()).moveTo(folder);
}