When using Relational Database Sources such as SQLServer, a very common senario is to create Forms that are related to each other (just how tables are related to each other in the database). At present we have to build separate forms and wire them manually and submit them one after the other in the right order so as to maintain referential integrity and so on. Also, when there is a one-to-many relationship a lot of work needs to be done. This become highly complex with complex relationships. As this is a very common and widely used senario, may I suggest to implement the following,
1. PowerApps should be able read the relationships defined in the Datasource (Just like SSRS Report Builder does) and build Forms accordingly with all the relationships wired in automatically.
2. In a one-to-many situation, PowerApps should build Main and Subforms accordingly.
3. All data should be submitted with a single Submit command.
Ofcourse, this could be extended to add many other useful features. But atleast this basic feature will save the day!