An earlier version of Dynamics 365/CRM introduced an inline edit view for Opportunity, Quote, Order and Invoice Products (line item products).
But the inline edit view was a “special” view that could not be edited, for example, to show additional fields.
But the editable grid control is available in the unified interface for line item products which means that custom public views can be used instead of the special inline edit view.
See https://docs.microsoft.com/en-us/dynamics365/sales-enterprise/editable-product-grid-forms