Yes. It is not a requirement to have a prior advertisement on BoligPortal or use BoligPortal's moving inspection service to create rental contracts.
You can freely manage rental contracts, moving inspection reports, and/or rent collection on BoligPortal without utilizing the other features. Of course, you are also welcome to advertise your rental property. All features are free to use on BoligPortal.*
When creating a rental contract without having advertised a rental property beforehand, you simply need to enter the relevant address of the property, and you are ready to create the rental contract.
*Using rent collection on BoligPortal may incur a fee charged by MobilePay.