Mdkart

This plugin for WordPress automatically add the rel=”lightbox[ID-OF-THE-POST]” to images linked in a post 
ID-OF-THE-POST is unique per post so all images per post are grouped in one lightbox set. 
Works also with the gallery Fonction of WP 2.7 and in comments
Doesn’t add the the files required for Lightbox (it only add the rel lightbox tag)! You have to insert yourself in your theme the required files or use a plugin like Lightbox 2 WordPress Plugin or Lightbox 2.3 plugin for WordPress
<h3>Changelog / Todo</h3>
0.4.1 
* Optimizing the code 
0.4 
* Now Compatible with the Gallery Fonction of WP 2.7 
* Adds also rel tag in the comments 
0.3 
* Correction of a bug that added rel tag on links done on img tags. 
0.2 
* Correction of a small bug described by Kristof Mattei. Thanks to him for the help!
Thanks to all who sent bug reports and ideas for improvements. 
Please send me a mail if I forgot you to mention here.

Add Lightbox

This plugin for Wordpress automatically add the rel="lightbox[ID-OF-THE-POST]" to images linked in a post

Diana van de Laarschot

The default custom menu in WordPress only allows adding a link that leads to a list of posts and pages belonging to a taxonomy (category, tag, etc). If you want to list the posts and pages themselves and if you want WordPress to do this automatically for you, then I hope you will find this plugin useful.
Also works for custom taxonomies and custom post types 
NEW: CPCM V3 now provides support for Full Site Editing with the Gutenberg Block Editor 
WARNING: Coming from version 1.x? There are breaking changes, read the changelog before upgrading.
<h4>Using it</h4>
Enable the plugin and go to either Appearance > Menus or Appearance > Customize or Appearance > Editor. Add a category (or other taxonomy like tag or custom) to the menu. Next, you can choose if you would like to replace the category by the posts or pages themselves.
For each Category in your menu, you now have the following extra configuration options:
<ul>
<li>Replace by posts in the category y/n; </li>
<li>specify the (maximum) number of posts you want to show for this item (max 10);</li>
<li>their ordering ascending or descending by Title, Date or Menu Order;</li>
<li>specify the title for the menu items. For this you can use %post_title, %post_author and other wildcards, see ‘Other Notes > Wildcards’. Default value: %post_title</li>
</ul>
<h4>Wildcards</h4>
You can control the title of the menu items generated by the plug-in with the following wildcards:
<ul>
<li>%post_title</li>
<li>%post_author</li>
<li>%post_date for the unformatted post date: 2012-11-10 18:14:23</li>
<li>%post_date() for a formatted post date with the following default formatting: November 10th, 2012</li>
<li>%post_date(<your formatting here>) for custom date formatting. Example: %post_date(l jS \of F Y, h:i:s A). See <a href="https://codex.wordpress.org/Formatting_Date_and_Time" rel="nofollow ugc">https://codex.wordpress.org/Formatting_Date_and_Time</a> for formatting options.</li>
<li>%post_date_gmt</li>
<li>%post_date_gmt()</li>
<li>%post_date_gmt(<your formatting here>)</li>
</ul>

Category Posts in Custom Menu

Dynamic menus: List all posts from a category in your menu. Also works for tags, custom taxonomies as well as pages and custom post types.

Add Lightbox vs Category Posts in Custom Menu