Michael Beckwith on "[Plugin: Custom Post Type UI] Can I use custom post type as taxonomy ?"

margeomthomas - You can acheive what you want with this plugin - https://wordpress.org/plugins/cpt-onomies/

I'm in the process of dissecting it for use with my own purposes which will allow me to use a CPT as Taxonomy more than once per post type. Basically that plugins works and works great for "attaching a post type to any other post type", however, it will only let you attach the CPT ONCE to each post type that you desire, and the way you attach the CPT to other post types forces them all to use the same verbiage and settings.

It works great for automatically building out related CPTs while keeping the "taxonomies" automatically "sync'd" between the various post types you attach CPTs to. It works great for that.

Maybe you're in the same boat as me too. I want slightly more complex capabilities: To be able to assign a CPT to another post type TWICE or more, with each instance having its' own values, labels, and so on. For example:

I have a CPT called "Voting Topic" and it has all kinds of custom fields and taxonomies specifically for voting topics. I have another CPT called "People" with its' own fields and taxonomies. I want 2 separate "taxonomies" (People CPT) assigned twice to the Voting Topic CPT, once for tracking "people who voted yes" and the other one for "people who voted no". It pulls from the same list of people, but the reason for selecting the people is different for each.

I know there are other ways to accomplish what I'm seeking, but I need the specific functionality offered by "merging" CPTs through the use of sortable taxonomies.

If you just need to dynamically link/sync CPTs through the use of sortable taxonomies, the plugin will be perfect for you out of the box.

If you're looking for "odd" functionality like me, then it's going to take some custom coding. There's no other options available. I've checked. :(

Michael Beckwith - It's a way to keep taxonomies always updated when dealing with complex structured data. You can basically use a post type as category, or a filter, or search term, and keep all occurrences of it across all of your related-but-separate post types and post data. It's actually quite useful and I was surprised to find that this isn't part of WP's backend functionality......and maybe not specifically assigning CPTs as taxonomies to other post types (that's just one way of achieving the end goal), but at least some better data linking method to help bring complex data to life. As useful and powerful as taxonomies are, without natively being able to "merge"/"sync"/"link" data from posttypes-to-taxonomies and from taxonomies-to-posttypes, they fall way short.