Hi Sigurður,
Do you have a Solution Manager in your Landscape? If yes, you can add a monitoring to this Content Server and then use the DBA Planning Calendar (CCMS transaction DB13 or DB13C) to schedule backups. If there is no Solution Manager, you can use the an ABAP system to monitor this MaxDB database and use the DB13/DB13C. In case no SAP system is available, you can use the operating system tools like the Windows Task Scheduler or Linux Crontab along with the dbmcli (Database Manager CLI).
Further information, please check the following SAP Notes:
1377148 - FAQ: SAP MaxDB backup / recovery
846890 - FAQ: SAP MaxDB database management
Regards,
Luis Darui