Where is the "add to cart" configuration? I'm trying to find the Add to cart form configuration for a product type in the UI.

When I export configuration, core.entity_form_display.commerce_order_item.TYPE.add_to_cart.yml contains the configuration for the Add to cart form, such as this (hiding quantity, creation date, and unit price):

content:
  purchased_entity:
    type: commerce_product_variation_attributes
    weight: 0
    settings: {  }
    region: content
    third_party_settings: {  }
hidden:
  created: true
  quantity: true
  unit_price: true


Where is the configuration page for this in the UI?  I keep clicking around and I cannot find it.
Go to the 'Order item types' page and click the "Manage form display" link for your order item type. You will then see a tab for the "Add to cart" form display.

For the 'default' order item type the url will be: /admin/commerce/config/order-item-types/default/edit/form-display/add_to_cart

There is an open issue for finding a more discoverable way to expose these settings.