How can define parts inside blocks ?
you can add another attribute using the Add Attribute button in the context bar below the selected Block.
The attribute will be added to the Properties compartment. If you change its type to a Block element defined in your model (e.g. NewAttribute1 : Block2), the attribute will be automatically moved to the References compartment. If you right-click on the attribute and choose Properties from the context menu and set Aggregation kind to Composite, the attribute will be displayed in the Parts compartment.