You can add custom property rows like this in the CustomizeDetails function:
TSharedPtr<IPropertyHandle> PropertyHandle = DetailBuilder.GetProperty("bStaticMeshReplicateMovement");
Category.AddCustomRow(Caption)
.WholeRowContent()
SNew(SProperty, PropertyHandle)
];
The property handle you search for has to be a UPROPERTY and should be a member of the class you are customizing
You can also add properties of external UObjects like this (provided you somehow get a reference of it in the CustomizeDetails function)
Category.AddExternalProperty(...)