Saving Pick, Group, & Rank responses to Embedded Data with Javascript

In the Survey flow, I've set up Group1a, Group1b, & Group1c as embedded data fields
I created a Pick, Group, & Rank item where the participant is to drag and drop their top three (of six) choices into a single group.
All I want to do is save the selected choices to the embedded data fields so I can use them later.
I'm really new to Javascript. I wrote the code below, which literally doesn't seem to do anything. I made another item which is multiple choice where I pipe into the options text the embedded data fields. When running through a preview, all three of the multiple choice option texts are blank. Any help would be appreciated.
I wrote the following code into the Pick, Group, & Rank item
Qualtrics.SurveyEngine.addOnUnload(function()
{
              /*Place your JavaScript here to run when the page is unloaded*/          
              let choicesall = this.getSelectedChoices();
              let choicesarray = choicesall.split(",");     
              Qualtrics.SurveyEngine.setEmbeddedData('Group1a', choicesarray[0]);
              Qualtrics.SurveyEngine.setEmbeddedData('Group1b', choicesarray[1]);
Qualtrics.SurveyEngine.setEmbeddedData('Group1c', choicesarray[2]);
});