Only your Published demands appear in the Marketplace; anything sitting in Draft, Closed or Cancelled is never shown to suppliers.
Each demand is listed on its own. There is no "all demands from this buyer" view a supplier can open. A supplier sees the buying company's name on the demand, but the company profile behind that name carries no list of the buyer's other demands — the profile is deliberately built without it.
Demands that turn into an order stay listed for a while with a Completed / Ordered badge. No new offers can be sent to them, and you can take them off the list yourself with Remove from marketplace. Demands whose deadline passed long ago drop out of the list on their own.
Suppliers work the Marketplace through category, delivery-country and currency filters. So a demand you publish does not land on a public notice board; it lands in the feed of suppliers who work with that material.
Sealed bidding applies per demand as well: no supplier sees a rival offer, a rival price, or even how many offers a demand has received.
Also asked as: Can suppliers see my draft demands? · Can a supplier list my past demands? · Can one supplier see everything my company has requested? · Does a closed demand stay in the marketplace?