Hey,
I think you miss understood the SDK for the Combo items options.
items is not an array of the Combo values, but it's an array if the values IDs so to make it work you need to have this in your "lang/en-US.json"
"properties": {
"gamemodule": {
"name": "Combo name",
"desc": "Combo description",
"items": {
"ABC": "ABC",
"123": "123",
"XYZ": "XYZ"
}
}
}
For more info check the COMBO PROPERTIES section in this page https://www.construct.net/fr/make-games/manuals/addon-sdk/guide/language-file
let me know if it does resolve your problem