I want to see the actual item name in the content editor. The display name being (mis)used by content editors which makes finding and linking items really hard.
For the content tree, select "Item Key" if you do not want the display names.
You can find the application options in the hamburger menu in the content editor, or in the control panel.
More information on the application options can be found here: https://doc.sitecore.net/sitecore_experience_platform/content_authoring/the_editing_tools/the_content_editor/the_application_options
More information on the personal settings available through the control panel can be found here: https://doc.sitecore.net/sitecore_experience_platform/content_authoring/the_editing_tools/change_your_personal_settings
These settings are to be set per user. If that is no option for you, you could try to automate this - John West wrote a post on setting an application option on login using the
loggedin pipeline (the post is rather old, so things might have changed since but it could give you guidance on how to do this)