Custom Element AddItem Not add Parameter in database

[bhp2810]

Are you requesting a feature, reporting a bug or ask a question?

What is the current behavior?

I used custom element dropdown and show data dynamically come from API. Below code used.

    .toolbox
    .addItem({
        name: "employee",
        isCopied: true,
        iconName: "icon-dropdown",
        title: "Employees",
        "renderAs": "select2",
        json: {
            "type": "dropdown",
            "renderAs": "select2",
            optionsCaption: "Select a Employee",
            choicesByUrl: {
                url: API_URL,
                path: "data",
                valueName: "id",
                titleName: "name"
            }
        }
    });```

I want to use select2 dropdown. so when I save this data for element in database it automatically remove "renderAs": "select2" option and it not saved in databse.

### What is the expected behavior?

Keep same as passed in code.

### How would you reproduce the current behavior (if this is a bug)?

#### Provide the test code and the tested page URL (if applicable)

Tested page URL:

Test code

### Specify your

* browser:
* editor version:

[tsv2013]

Your question is unclear to me. The "renderAs" is a custom property that is valid only if the corresponding custom widget (select2) is loaded.

If this property is lost during survey JSON serialization then it isn't known to SurveyJS since not defined

[mark-ellul]

@tsv2013 how do you make select2 known to the SurveyJS Creator?