I really understand the confusion but it is not a bug. We had lots of discussion on how to present the data source choices and apparently we can still make some improvements there.
A data grid that has 'association' or 'microflow' as data source does not have a search bar or a sort bar. Searching and sorting is based on database operations and these two data sources also work for objects that are not in the database.
However, you can choose 'database' as data source and still follow an association from the enclosing entity. This might be a little confusing, but it is the same difference as retrieving from database or by association in the microflow retrieve action. When you are retrieving from database you can still constrain on an association.
Retrieving 'by association' means that the most up-to-date (in memory value) of the association is used which can be different from the database.
Buttons are allowed for 'association' and 'microflow' data grids but no buttons are generated because the standard behavior does not make sense. If you fill a data grid with a microflow, what does 'Delete' mean? The next time the grid is viewed, the microflow will be executed again and those objects will be shown. Therefore, you have to create buttons yourself with the behavior you require.
I hope this helps.
Arjan, thanks for the clarification. But I am not sure if I can agree on the design choice for the over association option. Because I do think that new or delete have a specific meaning there.
Let’s take an example: I have an organization with people. If I show the organization with a data grid persons and I press new I would expect to create a new person for this organization. And the same you could say for deleting a person, although you can argue if you only want the reference to be deleted or the whole person. It now seems when designing forms with associations that it takes more work than pre 4.0. But maybe it is just getting used to it.