The default "Save" button is not available if you're not using the "replace textarea" method since CKEditor 4 and even in that case it's enabled only in wysiwyg mode.
This is just that plugin but removing those restrictions so you're allowed to use it and to hook into the command to do whatever you need.
Usage: In this builder remove the "Save" plugin and add this one. You're done. Now the button is always available and you can hook on the "save" event of the editor to save your data.
The recommended way to install all CKEditor add-ons is to create a custom build by using Online builder. To do that, click the Add to my editor button on the plugin page. When you are done, click the Build my editor button on the right side of the page to go to Online builder.
Note: This add-on is already selected to be a part of your current build.
Add-on installation instructions
If you want to add the plugin manually, you will need to:
Extract the downloaded plugin .zip into the plugins folder of your CKEditor installation. Example:
http://example.com/ckeditor/plugins/allowsave
Enable the plugin by using the extraPlugins configuration setting. Example:
config.extraPlugins = 'allowsave';
Download and configure all its dependencies, too.
Add-on dependencies
No additional dependencies.
Note: The plugin may have additional requirements. Check the add-on page and documentation for more details.