Creating a Task with Custom Fields via Deluge Function

Hi all,

I'm trying to create a task in Connect via a custom function I wrote as part of a Flow. The function works perfectly to create the task according to the documentation here: https://www.zoho.com/connect/api/create-task.html

I am using invokeurl.

I have some custom fields in my boards (just text fields for now) and would like to fill the fields when the task is being created, but I can't figure out how. All of the forums I've found are using json arrays, which have unsupported characters for a webhook. Is there a way to do this in a custom function like mine below? I have a custom field called "Participant ID" that I wold like to add. This is my working function:

void hl_connect_create_task(string inputBoardId, string inputTaskTitle, string inputsectionId, date inputstartTime)
{
// Create a map that holds the values of the task info that needs to be created
headerdata = Map();
headerdata.put("Authorization","Zoho-oauthtoken d92d401c803988c5cb849d0b4215f52");
scopeID = "scopeID=<myscopeid>";
boardId = "&boardId=" + inputBoardId;
titlespaces = inputTaskTitle.replaceAll(" ","%20");
title = "&title=" + titlespaces;
sectionId = "&sectionId=" + inputsectionId;
duedate = "&eyear=" + inputstartTime.getYear() + "&emonth=" + inputstartTime.getMonth() + "&edate=" + inputstartTime.getDay();
priority = "&priority=High";
position = "&position=7";
urltogether = "https://connect.zoho.com/pulse/api/addTask?" + scopeID + boardId + title + priority + sectionId + duedate + position;
res = invokeurl
[
url :urltogether
type :POST
headers:headerdata
connection:"<myconnectionname>"
];
info res;
}