kristarella

Copy or convert terms between taxonomies.
Taxonomies include categories, tags and any other custom taxonomies that may be present with your active theme and plugins.
This plugin, based on Categories to Tags Converter, allows you to copy (duplicate) or convert (move) terms from one taxonomy to another or to multiple taxonomies, while maintaining associated posts.

Taxonomy Converter

For starters, the plugin has deprecated code and produces errors on PHP7. Looks like the code hasn't really been touched all that much in many, many years.

The biggest problem is that when the terms are converted, the term descriptions are removed.

Doesn't include term descriptions

Copy or convert terms between taxonomies.

Dhanendran Rajagopal

Initial version of this plugin is a fork of https://wordpress.org/plugins/taxonomy-converter/.
Copy or convert terms between taxonomies.
Taxonomies include categories, tags and any other custom taxonomies that may be present with your active theme and plugins.
This plugin, allows you to copy (duplicate) or convert (move) terms from one taxonomy to another or to multiple taxonomies, while maintaining associated posts.
<h4>Large sites</h4>
Conversions run in batches over AJAX with a progress bar, so large term sets no longer time out. A Preview (dry run) button reports exactly what will happen — how many terms would be created, how many posts re-tagged, and how many source terms deleted — before you commit.
<h4>WP-CLI</h4>
For scripted or very large migrations, use the command line:
<pre><code># Preview copying two categories into post_tag
wp term-tax-converter convert 12 15 --from=category --to=post_tag --dry-run

# Convert (move) all categories into a custom taxonomy
wp term-tax-converter convert --all --from=category --to=topic --mode=convert
</code></pre>
Run <code>wp help term-tax-converter convert</code> for all options.

Term Taxonomy Converter

Copy or convert terms from one taxonomy to another while keeping their post associations.

Taxonomy Converter vs Term Taxonomy Converter