Zack Tollman

Surprisingly, WordPress does not provide a mechanism for sorting taxonomies by a custom defined order. Taxonomies can only be sorted by name or id. Custom Taxonomy Sort allows the average user a mechanism to define and display terms in a specified order. After installing Custom Taxonomy Sort, each taxonomy term will have the ability to have a “tax-order” value associated with it. This order is specified by doing the following:
<ol>
<li>Go to any taxonomy add or edit screen (e.g., wp-admin/edit-tags.php?taxonomy=category)</li>
<li>Fill in a numeric value for the “Order” field. By default, the order will be ascending, meaning it will sort from low to high (e.g., 1, 2, 3). These values can be added on the Add Taxonomy screen, the Edit Taxonomy screen, or through the Quick Edit panel.</li>
<li>Observe all of your terms automagically being sorted in the order you specified</li>
</ol>
Custom Taxonomy Sort automatically applies the sort order to all instances in which the terms are displayed. All you need to do is define that order.
<h4>Manual Mode</h4>
In addition to automatically sorting the terms, Custom Taxonomy Sort allows developers to override the automatic sort to offer finer control over how terms are displayed in different parts of WordPress. Manual mode can be started by changing “Automatic Sort” to “Off” in the Custom Taxonomy Sort Settings page (wp-admin/options-general.php?page=custom-taxonomy-sort-settings). Once “Automatic Sort” is switched to “Off”, the terms will no longer be sorted automatically by the custom order. Instead, the custom sort order can be envoked with a new parameter for the “orderby” argument. Custom Taxonomy Sort allows you to use the following argument to access a custom sorted list of terms using “get_terms”
<pre><code><?php get_terms('orderby=custom_sort'); ?>
</code></pre>
Voila! Now, your terms will only be sorted by the specified order in the places that you want it sorted in this order. All other instances of displaying terms will revert to WordPress’ default of sorting the terms by name. Additionally, you can specifically have the terms sort in ascending (‘ASC’; default; e.g., 1, 2, 3) or descending (‘DESC’; e.g., 3, 2, 1) order by adding the “order” argument.
<pre><code><?php get_terms('orderby=custom_sort&order=ASC'); ?>

<?php get_terms('orderby=custom_sort&order=DESC'); ?>
</code></pre>
<h4>Acknowledgements</h4>
<ul>
<li>Thanks to Jacob M Goldman for his excellent <a href="https://wordpress.org/extend/plugins/simple-term-meta/" rel="ugc">Simple Term Meta plugin</a>, which made programming the term meta quite simple. </li>
<li>Thanks to hydrowire <a href="https://wordpress.org/support/topic/plugin-custom-taxonomy-sort-error-in-quick-edit-post" rel="ugc">for pointing out a bug</a> fixed in 1.1.1</li>
<li>Thanks to “Mosey” for pointing out a bug with a situation in which order did not work for a custom taxonomy</li>
<li>Thanks to DUCK__BOY1981 for pointing out a bug where the column values where overridden inappropriately</li>
<li>Thanks to @martindj for pointing out a bug where the column value returned incorrectly</li>
</ul>

Custom Taxonomy Sort

Nice idea, but the plugin is quite severely broken and triggers nasty errors.
The problems do go away if you remove the function name clashes which are in the simple-term-meta.php file.
I'm guessing the errors have been occurring since WordPress 4.4 was released. So based on how long ago that was created, I'm assuming this plugin will never be updated :/



Broken

Custom Taxonomy Sort allows you to explicitly control the sort order of all taxonomy terms.

rdsteed

By default, the sort order for queries in WordPress is descending. This will produce posts in reverse chronological order, the desired result for most blogs.
In some cases, it may be desirable to have posts in ascending order. When activated, this plugin changes the default order from descending to ascending. This affects all queries (home page, archives, dates, etc). Deactivating the plugin returns the default order to descending.
IF YOU DON’T LIKE THE RESULT, IT’S THE THEME
How well this works out varies from theme to theme. Depending on a theme’s navigation labels for posts, things may or may not make sense. If labels are “Earlier” and “Later”, things will seem backwards. Some themes make sense either way. For example, in the “Twenty Fifteen” theme, “Previous” is above “Next”, suggesting list order rather than time.

Default Sort Ascend

This plugin changes the default order of queries generating posts from descending to ascending.

Custom Taxonomy Sort vs Default Sort Ascend