How to set/add default values for the item custom fields in invoice on mobile?

You can set default values for item custom fields in invoice by updating the product details.

Step 1: Go to Products and Select the product for which you want to add default values for the item.

Step 2: Click on the edit option from the top right corner

Step 3: Scroll down and enter the default value on the custom fields and Click update product

Step 4: Once updated, it will be shown like this.

Now, when you add the product to a invoice, the custom field will be pre-filled with the default value.