Hello @Brookie 

I think you can use something below below on flow designer to populate the checkbox label. You can do this for all your checkbox field.

var shortDescription = [];
if (fd_data._1__get_catalog_variables.acrobat) { // IF acrobat is checked then put Adobe Acrobat label in array
    shortDescription.push("Adobe Acrobat");
}
if (fd_data._1__get_catalog_variables.photoshop) { // IF acrobat is checked then put Adobe Acrobat label in array
    shortDescription.push("Adobe Photoshop");
}
return shortDescription.join("\n");

OR you can use the below script to get the variable from Requested Item record and populate the Label in short description dynamically

var shortDescription = [];
    var ritmVariables = fd_data.trigger.request_item.variables;
    for (var variable in ritmVariables) {
        var variableType = ritmVariables[variable].getQuestion().type;
        if (variableType == 7) {
            if (ritmVariables[variable] == "true") {
                shortDescription.push(ritmVariables[variable].getLabel());
            }
        }
    }
return shortDescription.join("\n");