Let the Product Quantity Take Care of Itself When Sales Reps Work with Opportunities
Where: This change applies to Lightning Experience and Salesforce Classic in Professional, Enterprise, Performance, Unlimited, and Developer editions.
Why: If the quantity is always 1 (as with a subscription) or is unknown until later, a default quantity of 1 helps reps add products faster.
How: To add a default quantity of 1, go to the Opportunity Settings page and select the option. If you contacted Customer Support to add the default value, the option is selected for you.
To hide the Quantity field, go to the Object Manager and remove the field from the Opportunity Line Item page layout and multiline editor layout.