Can a Campaign Manager include a Proposal in the Plan multiple times?

A Proposal in Inventory Management always corresponds to exactly one line. When this Proposal is adopted into a campaign's Media Plan, the following rule applies:

A Campaign Manager can only include a Proposal in the campaign plan once.

How can multiple Proposal lines be created in a campaign?

If you want to use a Proposal line multiple times in a campaign's Media Plan, you must provide multiple Proposals to the campaign.