Noby

The “Meta Functions Shortcode” Plugin installs the Shortcode ‘meta’. With it you can access the custom fields of your articles by a simple shortcode.
Shortcode Syntax: <code>[meta func="" name="" alt=""]</code>
The shortcode has three functions yet:
<ol>
<li>func=”url” 
 Displays a link using your custom field in “name” as the link target and “alt” as the caption. If “alt” is empty the link target is used as the caption.</li>
<li>func=”plain” 
 Simply displays the custom field in “name” as plain text. If the field is empty it displays the text in “alt”.</li>
<li>func=”img” 
 Inserts the image at the url in your custom field “name” into the article. The “alt” argument is used as the images alternative text attribute.</li>
<li>More functions in later versions of the plugin… Or extend the plugin on your own. See Extending the Plugin (under Other Notes) for details.</li>
</ol>
<h4>Example</h4>
<pre><code>[meta func="url" name="download_url" alt="Download here"]
</code></pre>
This little code in your article displays a link using your custom field “download_url” as the link target and “Download here” as the caption. If you leave the “alt” argument empty then it uses the link target as the caption.
The resulting html code is:
<pre><code><a href='{download_url}'>{alt}</a>
</code></pre>
<h3>Extending the Shortcode</h3>
<h4>Method 1: Hardcoded</h4>
You can extend the plugin by adding the PHP function
<pre><code>function meta_functions_shortcode_{func}($meta, $alt="") {
 return "your desired text or generated html content";
}
</code></pre>
by writing your own plugin file with the function in it. Be sure to replace {func} with your desired function name (will result in the parameter “func” in the shortcode). $meta will be the value of the custom field and $alt the “alt” parameter.
The function should return the text by which the shortcode will be replaced. For example the “_plain” function simply returns $meta or $alt if $meta is empty.
<h4>Method 2: In the admin panel</h4>
This method is more convenient. You can add new functions in the admin panel. For this go to the options page called “Meta Functions Shortcode”. 
Here you can enter a new function name, specify parameter names and set the output html code with the parameters.
Example:
<ul>
<li>Function Name: link</li>
<li>Function Parameter Names: link_url, link_caption</li>
<li>Function Result Code: <code><a href='{link_url}'>{link_caption}</a></code> </li>
</ul>
If you now enter the shortcode [meta func=”link” link_url=”download_url” link_caption=”download_caption”] then in the article/page 
it will be replaced by <code><a href='contents of custom field download_url'>contents of custom field download_caption</a></code>.

Meta Functions Shortcode

The “Meta Functions Shortcode” Plugin installs the Shortcode ‘meta’. With it you can access the custom fields of your articles by a shortcode.

Scott Reilly

By default, WordPress only allows 30 custom field names/keys to be listed in the dropdown selection ‘Name’ field when writing a post or page. If you, or the plugins you use, make use of a lot of custom field key names, you may surpass the default limit resulting in some custom field keys not being listed. This may force post authors to manually type in custom field key names if they aren’t listed, which increases the chances for naming errors (typos, or not using the precise key name that is needed). This may also cause some authors concern wondering where previously used custom field keys have gone since they aren’t listed.
This plugin increases the limit to 200 custom field key names.
There is no settings page to customize the default value. If you’d like to list some number of custom field key names other than 200 (say, for example, 100), you can do so in either of two ways:
<ol>
<li>By editing your wp-config.php file and at the end adding a line such as: 
define( ‘CUSTOM_FIELD_NAMES_LIMIT’, 100 ); 
-or-</li>
<li>Somewhere — ideally in a mu-plugin or site-specific plugin, or less ideally your active theme’s functions.php file — hook the ‘c2c_list_more_custom_field_names’ filter and return the number you’d like to use: 
add_filter( ‘c2c_list_more_custom_field_names’, function ( $limist ) { return 100; } );</li>
</ol>
Note: This plugin has no effect for users who make use of the block editor (aka Gutenberg) introduced in WordPress v5.0 because that editor does not directly expose custom fields in the interface.
Links: <a href="https://coffee2code.com/wp-plugins/list-more-custom-field-names/" rel="nofollow ugc">Plugin Homepage</a> | <a href="https://wordpress.org/plugins/list-more-custom-field-names/" rel="ugc">Plugin Directory Page</a> | <a href="https://github.com/coffee2code/list-more-custom-field-names/" rel="nofollow ugc">GitHub</a> | <a href="https://coffee2code.com" rel="nofollow ugc">Author Homepage</a>

List More Custom Field Names

Allows for more existing custom field names to be listed in the dropdown selection field when writing a post.

Meta Functions Shortcode vs List More Custom Field Names