This is possible when using the Default Explode. When activating the default explode of the top level assembly, also the default explode of the subassemblies are triggered.
Tip 1: Existing exploded views can be saved as Default Explode, no rework has to be done.
Tip 2: The default exploded state on the top level can be saved under a different name. This way in combination with Tip 1, multiple exploded states can be transferred to the top level (via the Default Explode)