how to select all values in the list dropdown automatically in jira?

[rakesh rocckz]

I created a rest endpoint which runs the "GET' request and I also created a behavior script which converts the multiline text field to dropdown(convertToMultiSelect). I am using below method which converts the multiline text field to the dropdown. but I want to default show everything instead of a dropdown. how can I achieve this without selecting any value from the dropdown it should automatically show everything from the drop-down to multiline text field?? please help me out