Is there a way to add a tab on the publish form within the Template Manager like it is with the Channels?
For example, the Template Manager has the default Edit, Notes, Settings and Access form tabs. I wanted to add another from my custom module.
Is this currently possible within the core API?
You can create your own module to add a TAB in channel entries. You need to follow the documentation of creating a module.
This URL will help you to create a module. Your structure should be like given image below:
On your UPD file install function, remember to put has_publish_fields value as y. otherwise your data you want to display in tab will show on publish Tab.
