You can choose the internal storage or SD card right after the installation of Sygic GPS Truck & Caravan Navigation:
If you would like to move an already installed Sygic GPS Truck & Caravan Navigation to a different storage, then it is necessary to uninstall the app, delete/cut any leftover folders, and then install the app again.
Sygic GPS Truck & Caravan Navigation uses two different folder paths - one for internal memory and one for the SD card.
Internal memory / Android/data/com.sygic.truck/files/SygicTruck
SD-card / Android/data/com.sygic.truck/files/SygicTruck