You can remove a custom item from a page layout, using the New Quote button on the Opportunity page.

1. Navigate to user name > Setup > App Setup > Customize > Opportunities > Page Layouts.
2. Click Edit, which is next to Opportunity Layout.
3. Click Related Lists to display the Related Lists objects.
4. Click the Remove Related Lists icon on the Quotes related list.
5. Click Buttons to display the buttons that you want to remove.
6. Drag the New Quote button from the Custom Buttons area to the Buttons list.

   

7. Click Save.