This can be done in the cluster management console for a Dynatrace Managed cluster. Navigate to the environment which you want to increase the storage retention:
It appears you are on the right screen - how much space is left on the node(s) in your cluster? I see you are using 38.13 GB of storage for transaction data - is there anymore allocated in the filesystem you are using for that storage?
Yes Mija, that's exactly right. Once you select a higher amount of time for transaction storage it will begin working to build a rolling window for that amount of time. You can also see the current number of days that are being stored on the environment's overview page.
Hope this helps!