In central admin, there is option to add new group and action in "Operation" page like :Topology".
Here is the xml file that can added new custom group in the central administration.
You can installed as new feature for that and activated features in site feature.
feature.xml
<Feature Id="56FD5FEC-4FE9-4970-B1B6-20580B2ECD1B" Title="Test Group Page"
Description="Test Group Page." Version="1.0.0.0" Scope="Web" Hidden="false"
DefaultResourceFile="core" xmlns="http://schemas.microsoft.com/sharepoint/">
<ElementManifests >
<ElementManifest Location="element.xml" />
</ElementManifests>
</Feature>
element.xml
<Elements xmlns="http://schemas.microsoft.com/sharepoint/">
<CustomActionGroup Id="{6C3A6045-5F34-4203-80E7-C9DD90801835}" Title="Test Group" Location="Microsoft.SharePoint.Administration.Operations" Sequence="100" />
<CustomAction Id="{EA6E9E68-32C6-47f2-9CF3-07D7A496623D}" Title="Test Page" Location="Microsoft.SharePoint.Administration.Operations"
GroupId="{6C3A6045-5F34-4203-80E7-C9DD90801835}"
RequireSiteAdministrator="TRUE"
Sequence="10">
<UrlAction Url="/_controltemplates/ApplicationPage.aspx"/>
</CustomAction>
</Elements>
Links :
http://blog.thekid.me.uk/archive/2007/06/23/sample-editcontrolblock-customaction-for-sharepoint.aspx