Bage

Modal windows are interesting way to include extran information on a page. <a href="http://www.onextrapixel.com/2014/06/25/create-modal-windows-that-can-be-morphed-from-anything-with-jquery-adaptive-modal-js/" rel="nofollow ugc">adaptive-modal.js</a> makes it beautiful. You can use this little plugin which uses the same jQuery plugin to creae modal windows easily in any page or post or even on a widget uisng shortcode.
I have also added another functionality into this plugin, which will let you to embed your modal content into your post a page directly.
<h3>Usage</h3>
Upon activation, the plugin will create a custom post type called ‘Modals’. Where you can add your content, which later you can use it on a modal or embed directly into your page or post.
<ol>
<li>[modal]</li>
<li>[block] </li>
</ol>
<h3>modal</h3>
the ‘modal’ shortcode is to create modal windows.
For now the [modal] shortcode comes with four attributes.
id 
Your modal id. eg: [modal id=2]Click here[/modal]
data 
If your modal only going to have just text, you can directly add the content in the shortcode. eg: [modal data=”This is my modal content”]Click here[/modal]. This shortcode is much useful when you want to add a modal window to a word in a paragrap without braking the paragrap.
<pre><code>note: you cannot use both id and data in the same shortcode
</code></pre>
background 
This is to style the link and the modal window background. Have to specify a valid color. eg: [modal id=2 background=”#DDDDDD”]Click here[/modal]
color 
This attribute is to change the color of the link. eg: [modal id=2 background=”#DDDDDD” color=”#000000″]Click here[/modal]
<h3>block</h3>
The ‘block’ shortcode is to embed your modal content into any page or post. It only has one attribute.
id 
id of the modal post type post.
<pre><code>note: both block and modal shortcodes uses the same Modals custom post type.
</code></pre>

Flexible Modals

Flexible Modal is a very simple plugin to add modal windows to your WordPress content using shortcodes.

Andrei Baicus

This plugin adds a customizable Popup Block to the WordPress block editor.

Popup Block

Works fine in Chrome and Edge, but can't get Exit Intent to reveal the box using Firefox.

Exit intent not working in Firefox

A popup/modal block for the WordPress block editor.

Flexible Modals vs Popup Block