In your Proposal Settings, you can choose to hide quantity, unit price on line item total on proposals:
By default, these will be turned on so that they each SHOW on proposals.
Note, you can always override the settings on an individual proposal. When creating or editing the proposal, you can check/uncheck these checkboxes:
A common use case might be to hide quantity and unit price. If those were hidden, the proposal (web view and PDF) would be updated so that the quantity and unit price columns do not appear. For example:
Note, when editing the proposal you will still see all columns; however, the customer will not see them on the URL/PDF.