How to add a widget code to a Header/Navigation Button

Hello! I'm looking for a solution to add a widget code to a header button.

website: https://millandmainrestaurant.squarespace.com/reservations 
Does anyone know how to do that?
Thank you!

the code I have: 

<div style="text-align: center;"><a href="https://resy.com/cities/kerhonkson-ny/venues/mill-and-main" id="resyButton-ZMLifg9xYpLYfaOawWuqJ">Book your Mill & Main reservation on Resy</a></div>


<script src="https://widgets.resy.com/embed.js"></script>
<script>
resyWidget.addButton(document.getElementById('resyButton-ZMLifg9xYpLYfaOawWuqJ'), {"venueId":72291,"apiKey":"sAqIjRUrrfAL9EzFQNEQjH6gTP64obBX","replace":true});
</script>

@ChristinaB Hi! I haven't been able to test the code on your site since it requires a custom script to set the ID to the header button. Please try adding this code under Website > Settings > Advanced > Code Injection > Header.

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.7.1/jquery.min.js"></script>

<script>
$(document).ready(function() {
    var link = $('.header-actions-action .btn');
    link.attr('href', 'https://resy.com/cities/kerhonkson-ny/venues/mill-and-main" id="resyButton-ZMLifg9xYpLYfaOawWuqJ');
    link.attr('id', 'resyButton-ZMLifg9xYpLYfaOawWuqJ');
});
</script>

<script src="https://widgets.resy.com/embed.js"></script>
<script>
resyWidget.addButton(document.getElementById('resyButton-ZMLifg9xYpLYfaOawWuqJ'), {"venueId":72291,"apiKey":"sAqIjRUrrfAL9EzFQNEQjH6gTP64obBX","replace":true});
</script>

Let me know how it goes. Thanks! 

@Lesum It didn't work 😞
 I want it to show up as a popup like on this page, I embedded the code I mentioned earlier  https://millandmainrestaurant.squarespace.com/reservations

@ChristinaB I only added the URL and ID to the button based on the information you shared in your script. How it is supposed to pop up on the page depends on the third-party platform where you got the embed code from. Please check if everything is set up correctly there, and if there is an issue, try contacting their support.

@Lesum Did you check the link I sent you?
https://millandmainrestaurant.squarespace.com/reservations password: 0000
is there a way to add the same functionality to the header button as the red button one?

@ChristinaB Yes I checked your link and wrote the code solution based on your website header. However, code I shared isn't working as the red button is opening the popup inside an iframe. 

You can try adding a link under you main navigation. Then add the embed code inside the link URL. 

Can you send password?

this would be helpful.  Any progress?