If you choose not to take your earned holiday during the relevant holiday year, the money remains reserved for you. In Denmark, holiday pay is managed through the Danish Holiday Act. This means your employer must transfer your earned holiday pay to the Danish Holiday Fund (Feriepengepenge). This ensures that your money is protected even if your relationship with the employer ends.
If you leave your job before the money is paid out as salary, you do not lose it. The funds are securely held by the Holiday Fund until you either request to use them or reach a point where the fund pays them out to you. You can always log in to borger.dk to view your current balance and see when the money will be made available for use.
Please note that holiday pay is strictly for holiday purposes. You cannot ask your employer to pay out holiday pay as regular salary while you are still employed. The money stays saved in the system until you take your time off or fulfill the requirements to claim it through the official holiday fund processes.