Also if you wish to edit the XML witch i advise against. Each component has a special property (or a pair of properties) when it belongs to a group or to a tab.
For tabs:
[code:1kdn9kpg]
componentTabName="tabComponent" — the name of the Tab component
componentTabId="0" — the index of the tab within the Tab component
[/code:1kdn9kpg]
For groups
[code:1kdn9kpg]
componentGroupName="groupComponent" — the name of the group Component
[/code:1kdn9kpg]
You can see that in the Utility tab on the property pane, it’s in the XML of the <component /> element. Also please remember that changing those properties will affect their position, the rectangle that the component has will be relative to the group/tab component, not to the panel anymore, so remember to change the rectangle too.