The Developer Mode option on the Preferences screen in Myo Connect gives debugging and development options for Connector scripts listed in the Application Manager.
When you enable Developer Mode, the Debug Console is enabled. This gives Connector scripts a place to display logs and information.
Scripts which use the Debug Console are identified by a "DEV" icon label in Application Manager.
Developer Mode also allows you to add Connector scripts directly from the folder in which they are saved, instead of automatically copying them to the default folder used by Myo Connect. This also allows scripts to be refreshed using the reload button.