This feature helps in creating both Firewall and Program Expert Rules, by allowing you topre-configure Locations, Protocols, and Times that your rules will use. The time spent exploring and creating Groups and how to implement them in your Firewall and Program Expert Rules will give you a much better insight as to how Expert Rules work and can be implemented.
The ZAP help file has a good overview of Expert Rules and should be your first resource for any questions the may come up. Firewall Expert rules are found under Firewall protection starting with the subsection Understanding expert firewall rules. Program Expert Rules are found in the Program control section starting with the subsection Creating expert rules for programs.
One thing you must remember is how the Expert Rules are applied. Firewall rules are processed before Program rules.
I hope this gets the ball and creative electrons rolling about this new feature.