Weil es einfacher ist, zitiere ich einfach mal die engl. FAQ. Zu finden hier:
http://shadowrun4.com/resources/faq.shtml
When can you break up a skill group into its component skills? Can you break it up during character creation? Can I break apart a skill group in order to buy a specialization for one of the skills?
You can break apart a skill group whenever you want—as long as the GM allows it. We advise against breaking apart skill groups during character creation in order to keep it simple and counter min-maxing. Any time you improve a single skill within a skill group or add a specialization to one of those skills, that skill group no longer exists.
Can you regain a skill group if each of the component skills are raised to the same level? What if one of the skills has a specialization?
Yes, if a skill group's individual skills are raised to the same rating, those skills can be treated as a skill group from that point on—any specializations, however, are lost (specializations and skill groups are simply incompatible; you can have one or the other, but not both).
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In unserer SR4-Runde brechen wir die Fertigkeitsgruppen immer erst nach der Generierung auf. Das Ganze hat aber keinen besonderen Hintergrund. Ich persönlich finde es auch unproblematisch die Gruppen schon während der Char-Erstellung aufzubrechen. Aber wie du liest, eine eindeutige Regelung gibt es da auch von offizieller Seite her nicht.
Grüße
Lars