The seriousness of the device vendor is shown by the fact that its instructions were scanned and a pdf was made. There is of course nothing in it as far as navigation settings are concerned

You should look very carefully through the settings menu of the device itself. Is there an item "navigation path" somewhere at all.
It may not exist, it may be hidden and it may be locked.

Should be under
1. Touch the upper left corner to display the main menu.
2. Touch [ Settings ].
The settings menu is displayed.

Adjust General Settings
1. Touch [ General ], if necessary.
2. Touch to highlight a setting.
3. Touch to display/select an option.
4. Touch blank area of the screen to exit.
>>>
Radio region
Sensitivity
Blackout
Dimmer mode
OSD
Beep
Calibration
GPS path setup