The source type of the member is added as an extension to a newly created member. It is this extension that determines what editor is launched when you double-click on a member.
If you right-click on a member and select Open (or double-click on the member), the default editor registered for that extension type is launched. By default, the Remote Systems LPEX Editor is registered as the default editor for all source types that are listed in the New IBM® i Member wizard.
If you right-click on a member and select Open With, the menu displays the default editor associated with the given extension type, along with Default Text Editor and System Editor. The Default Text Editor is a basic, general purpose editor. The System Editor menu item launches the system editor registered with the operating system for a file with this extension.