To hold bill:
Go to POS & PAYMENT
Add orders to your current sale as per usual on the Point of Sale page
To hold the bill, press and hold the 'PAY' button
Key in a 'Hold Bill' note e.g. Customer's name
Here's a video guide from Step 1 to 4:
When the customer is ready to pay, you can pull out the saved order by selecting the top left 'Hold Bill' icon