1) sharepoint online with parent/child data: Example an office-supplies request form. User selects items from inventory list and creates an order with multiple items which goes for approval. We join inventory, order, items tables together to build this. in SPO.
2) document associated with SPO list: Example, an event booking tool where the travel agent attaches ticket PDFs and hotel confirmation email documents to individual events in a list of travel requests.
I'm marking this completed because it falls into the Template and Sample apps released which do illustrate these scenarios (Note that templates based on Excel can often also be replicated in SharePoint; where the tables in Excel are replaced with lists in SharePoint). It is possible that other sample templates based on SharePoint connectors would be added in the future, but this is undetermined at this time.
However, it is definitely planned to further extend what's available today to help app-makers worknig with SharePoint connectors. In the meantime, I'd like to direct you to these resources:
As of now here are some helpful resources (feel free to direct message me if you need additional assistance). I am always willing to plan new blogs based on your requirements.