in VMAN there's "Average Host CPU Usage by cluster" trend only. But it's easy to create your own trend. Try following those steps:
1. in Explore - Content menu focus on "Average Host CPU Usage by cluster" trend and press Configure button
2. on Criteria tab replace "/hostServer/cpuUtilization/latest/text()" by "/hostServer/memoryUtilization/latest/text()" (or select host.memload.latest attribute in list of attributes)
3. press "Save As" button and use "Average Host Memory Usage by cluster" as the trend name
From that time you will get percentual average Host Mem usage by cluster. Please keep in mind that the new trend doesn't display values in the past.
Let us know if this solution hits your needs. Thanks.