How to add multiple fields in one group

I am looking into the panel extension solution, and set up a magic group referenced by the official example, the magic group works fine. But I have a question, how to add multiple fields in this group. I tried to do it, there is an error thrown here:

//the guid and code text field need to be displayed on the property panel together
import guidProps from './parts/GuidProps';
import codeProps from './parts/CodeProps';

const LOW_PRIORITY = 500;

export default function IdentitiyPropertiesProvider(propertiesPanel, translate) {
    this.getGroups = function (element) {
        return function (groups) {
            groups.push(createIdentityGroup(element, translate));
            return groups;
    propertiesPanel.registerProvider(LOW_PRIORITY, this);

IdentitiyPropertiesProvider.$inject = ['propertiesPanel', 'translate'];

function createIdentityGroup(element, translate) {
    const identityGroup = {
        id: 'identity',
        label: translate('Identity Properties'),
        //entries: guidProps(element)                //only one property works fine
        entries: [guidProps(element), codeProps(element)]                //this will throw an error message
    return identityGroup;

The error is below:

unhandled error in event listener DOMException: String contains an invalid character

It seemed that the entries can’t be an array in createIdentityGroup method. If I only set one property, it works fine. Hope someone can make suggestion here. Thanks

For further assistance, please share a CodeSandbox that reproduces your issue in a way that we can inspect it.

Thanks your reply, when I import property panel extend project into codesandbox from github,
bpmnjs property panel extension
there is an error occurred although I havent done any modification. I have created a code sandbox sample project here.


Cannot read properties of null (reading 'appendChild')
new Modeler
  16 | 
  17 | var container = $("#js-drop-zone");
  18 | 
> 19 | var bpmnModeler = new BpmnModeler({
     |                  ^
  20 |   container: "#js-canvas",
  21 |   propertiesPanel: {
  22 |     parent: "#js-properties-panel"
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@Niklas_Kiefer , Thanks your response, I have found the reason that in magic property, it returns array object, I put their code here.

export default function(element) {

  return [
      id: 'spell',
      component: Spell,
      isEdited: isTextFieldEntryEdited

It already an array object, if I change it to a simple object, it will work fine.