pflonk

This plugin allows you to pass content to any sidebar from the page without using userdefined fields. Therefore it is possible to use the WYSIWIG-editor of your choice.
How it works: 
This plugin comes with a new enclosing shortcode [sidebar_content][/sidebar_content] where you can place any content, you want to have displayed in the sidebar. You will be able to use other shortcodes within this shortcode to use galleries, videos or any other stuff in the sidebar of your choice.
Additionally there will be a new widget which you can insert into the sidebar you want to have the content displayed. 
If you would like to pass content to an existing sidebar, there is another possibility using the [insert_sidebar_content] shortcode in any place you want. You are able to pass an id and/or a class to that content, to be able to style it with css as you like. This happens by simply adding: 
[insert_sidebar_content id=”yourID” class=”yourClass”] to the shortcode. You can of course use just one or none of them. If you do not specify any custom class or id, there will be a standard class and id called “insert_scfs” applied to the content, wrapped in a div.
<h3>Features</h3>
<ol>
<li>Widget</li>
</ol>
<ul>
<li>optional title (if empty, no tag will be generated)</li>
<li>optional title tag (default h3)</li>
<li>optional title tag CSS-classes</li>
<li>optional content-wrapper tag (default div)</li>
<li>optional CSS-classes for content-wrapper tag</li>
<li>optional CSS-id for content-wrapper tag</li>
<li>default values for every of the above possibilities</li>
</ul>
<ol>
<li>Shortcodes</li>
</ol>
2.1 Content-Enclosement
<ul>
<li>[sidebar_content]CONTENT[/sidebar_content] for use on any page</li>
</ul>
2.2 Widget-Display
<ul>
<li>[insert_sidebar_content id=”yourID” class=”yourClass”] to display the content from the [sidebar_content]-Shortcode in any widget you like</li>
<li>applicable id and classes</li>
</ul>
You will find further support on http://dev.offensichtlich.net
<h3>Thanks</h3>
Thanks to the authors that provided information about how to implement this simple little function that I just put together:
Ryan Bosinger 
http://www.ryanbosinger.com/boztown/2013/03/07/wordpress-custom-content/
1st-tec.de 
http://www.tipps.1st-tec.de/wordpress/39-wordpress/sidebar-widgets/152-eigene-widgets-fuer-die-sidebar-erstellen.html

Sidebar-Content from Shortcode

This Plugin enables passing content to any sidebar from the page without using userdefined fields. Therefore it is possible to use the WYSIWIG-editor  …

Amit Singh

oceanwp

Generates an unlimited number of sidebars and place them on any page you wish. Go to Theme Panel > Sidebars to create your custom sidebars. 
This plugin requires the <a href="https://oceanwp.org/" rel="nofollow ugc">OceanWP</a> theme to be installed.

Ocean Custom Sidebar

This little free plugin allowed me to easily add any Elementor Library Item to any menu in any area. Show video's, products, forms anything you like in your menu's of sidebars.

Really, REALLY useful!

Do NOT underestimate it's power!

Generates an unlimited number of sidebars and place them on any page you wish. Go to Theme Panel > Sidebars to create your custom sidebars.

Sidebar-Content from Shortcode vs Ocean Custom Sidebar