All the Oracle-native metrics fetched by Oracle database insights are available for custom charts.
Please have a look at the below link for more insight.
The part that you are familiar with is in Tecnologies on the left-side menu, then the "Oracle Database" tile, then the "Oracle Database" group that has a "DB Insignts" in the Source column. You click the associated Oracle database/device and it should take you to a page similar to:
Regarding metrics, they are also available, and do serve for some neat dashboards. In Custom charts, select Technologies, and then "Oracle", and you will get the list:
In Metrics, it's more or less the same, just filter by Oracle: