1. Go to Settings.
2. Select the General Settings tab.
3. In the POS Product Grid section, enter the default category ID number in the field under DEFAULT POS CATEGORY ID.
4. Scroll down and press Save.
Assign a Default Category in the Frontend
Assign a specific category as the default category in the frontend of the POS. The screen will always default to the category in this setting, all you need to do is input the category ID number.