AWS/RDS Disk Usage: add monitoring of FreeStorageSpace

Dear all,
We will be interesting to see the status of our AWS /RDS Disk Usage, Free Storage but the current checkmk metric does not fit our requirements:

The following are the checkmk metrics :

AWS/RDS %s Binary Log Usage
uses the metric BinLogDiskUsage
AWS/RDS %s Transaction Logs Usage
uses the metric TransactionLogsDiskUsage
AWS/RDS %s Replication Slot Usage
uses the metric ReplicationSlotDiskUsage

But according to AWS docs : https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/rds-metrics.html
The metrics is : FreeStorageSpace.

Do you think it will be possible to adapt the AWS/RDS metrics ?

Thanks
BR
Virginie