I use Flic with Leviton smart switches but I needed to use a custom setup on my Flic hub using the SDK.

If you are interested in that approach you can use the sample code below.

The const at the top need to be replaced with IDs specific to your setup. I think I can dig up a postman collection on how to get those IDs which I created based on this library. It is on a different computer, but I think I can get access to it in a few days.

// main.js
var buttonManager = require("buttons");
var http = require("http");

const L_DUSTIN_ID = "<LEVITON ID 1>";
const L_CAT_ID = "<LEVITON ID 2>";
const L_MASTER_ID = "<LEVITON ID 3>";
const FLIC_BUTTON_ID = "<FLIC BUTTON ID>";
const ACCESS_KEY = "<LEVITON ACCESS KEY>";
function toggleSwitch(switchId) {
	  console.log("toggling: " + switchId);
	  // Get current Switch Status.
	  http.makeRequest({
			url: "https://my.leviton.com/api/IotSwitches/" + switchId,
		  method: "GET",
		  headers: {"Content-Type": "application/json", "authorization": ACCESS_KEY}		
		}, function(err, res) {
			
			if(res.statusCode != 200) {
				console.log("request status: " + res.statusMessage);
			} else {
				// Toggle the switch
					http.makeRequest({
						url: "https://my.leviton.com/api/IotSwitches/" + switchId,
						method: "PUT",
						headers: {"Content-Type": "application/json", "authorization": ACCESS_KEY},
						content: JSON.stringify({"power": JSON.parse(res.content).power == "ON" ? "OFF": "ON"}),		
				}, function(err, res) {
					
				});
			}
		});
	
}

function handleButton(obj){
  if(obj.isSingleClick) {
		toggleSwitch(L_DUSTIN_ID);
	}
	
	if(obj.isDoubleClick) {
		toggleSwitch(L_CAT_ID);
	}
	
	if(obj.isHold) {
		toggleSwitch(L_MASTER_ID);
	}
}

buttonManager.on("buttonSingleOrDoubleClickOrHold", function(obj) {
	var button = buttonManager.getButton(obj.bdaddr);
	if(button.uuid == FLIC_BUTTON_ID) {
		handleButton(obj)
	}
});

console.log("Started");