Use case

Currently, ExpansionTile childrenPadding property is a nullable property that users can set or default to EdgeInsets.zero, if developers want to follow a specific design they need to set childrenPadding every time.

Proposal

Since ExpansionTile is a much more specific widget than ListTile, it should have its own ThemeData so developers could globally set those styling properties. Of course, it could also inherit from ListTileThemeData since there are common properties between them like contentPadding.