Could you tell me what the "System" display in views is? (shown in red)
I suppose it's a presentation which is only available programmatically, but I'm not 100% sure.
Thanks.
The Views System module extends the Views module and allows to create customized lists (pages, blocks) of modules, themes, and theme engines that are or have been installed in Drupal's file system
System
display should not be available when the Views System module is not installed. However I can see without ever having installed that module, therefor I do not believe this is an answer to the question.
Commented
Jun 29, 2016 at 13:05
Today I was in the same situation, so I decided to look and this is what I found:
So, for anyone stumbling upon this, 'system' displays are only to override core views (which you do through the System Path Settings area in the Advanced section of views) and I should just be using a page display with a path that begins with '/admin/' if I want to make custom admin views.
Here is the link: https://www.drupal.org/node/2539256#comment-10150524
The answer is that this is a style exposed by the Commerce Backoffice module. It's a heavily-modified version of the "Page" display style option, with the ability to replace existing menu paths with views.
Source: https://www.redbottledesign.com/blog/whats-drupal-views-system-display-style
And indeed when looking in the commerce backoffice module repository we can see the display plugin defined here: http://cgit.drupalcode.org/commerce_backoffice/tree/includes/views/plugins/commerce_backoffice_content_plugin_display_system.inc