You can also use the below XML and can also try it after replacing Entity="String" with Entity="false". This XML defines what will be displayed in the main pane of the application when selected.
<SubArea
AvailableOffline=["0" | "1" | "true" | "false"]
CheckExtensionProperty="String"
Client=["All" | "Outlook" | "OutlookLaptopClient" | "OutlookWorkstationClient" | "Web" ]
Description="String"
DescriptionResourceId="String"
Entity="String"
GetStartedPanePath="String"
GetStartedPanePathAdmin="String"
GetStartedPanePathAdminOutlook="String"
GetStartedPanePathOutlook="String"
Icon="String"
Id="String"
License="String"
OutlookShortcutIcon="String"
PassParams=["0" | "1" | "true" | "false"]
ResourceId="String"
Sku=["All" | "OnPremise" | "Live" | "SPLA"]
Title="String"
Url="String">
<Titles />
<Descriptions />
<Privilege/>
</SubArea>