Add combo-box to BPMN-JS panel properties

I studied Properties panel extension example

I can customize the example to add other properties such as spell2 and spell3 and … .

But I need to add a drop down list, in properties panel extension.
Could any one show me some hints or examples?

More details: I need to have a combo-box with some options, to choose from the list and set the selected value to spell property. In the Bpmn-js example, I can type/write a value in the input field, then it is assigned to spell property. How about choosing a value from a select list?

This is my customized magic.json, I know it has many issues but can’t manage it:

{
  "name": "Email",
  "prefix": "email",
  "uri": "http://email",
  "xml": {
    "tagAlias": "lowerCase"
  },
  "associations": [],
  "types": [
    {
      "name": "BewitchedStartEvent",
      "extends": [
        "bpmn:ServiceTask"
      ],
      "properties": [
        {
          "name": "sender",
          "isAttr": true,
          "type": "String"
        },
		{
          "name": "recipient",
          "isAttr": true,
          "type": "ComboBox"
        }
      ]
    },
	{
      "name": "ComboBox",
      "properties": [
        {
          "id": "1",
	  "value" : "First",
          "type": "String"
        },
        {
          "id": "2",
	  "value" : "Second",		  
          "type": "String"
        }		
      ]
    }
  ]
}

And after that I must config MagicProps.js but can’t manage a drop down list.

Can’t you use the existing SelectEntry for this one?

Example: bpmn-js-properties-panel/ImplementationType.js at 0.x · bpmn-io/bpmn-js-properties-panel · GitHub

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