You can access your Plugins Page at bubble.io/your_plugins and create a new plugins there. This page is also where you'll be able to define your Contributor profile, set your logo, connect with Stripe if you're selling templates or plugins, etc.
Clicking on the edit icon for a plugin will take you to the Plugin Editor.
The plugin editor follows a similar structure to the application editor, structured in 7 tabs.
The General Tab is where you define how the plugin looks in the library and some keywords to improve its visibility
The Shared Tab is where you can define some shared technical aspects of the plugin (shared HTML header, assets, etc.)
The API calls Tab is where you add new API connections and authentications method. It is very similar to the API connector.
The Elements Tab lets you create new Bubble elements.
The Actions Tab lets you add actions that can be used in Bubble workflows.
The Settings Tab lets you publish your plugin, see the version history and pick a license
The Review Tab lets you see reviews from users.
The plugin editor automatically saves your work as you are modifying the plugin. Note that the editor does not support multi-user editing.