StaticSyncSource
The UserFieldMappingSyncSource can be used to add static properties or claims to the sync process:
<StaticSyncSource name="Static">
    <Property name="test1">helloworld</Property>
    <Property name="test2">helloworld2</Property>
    <Claims>
        <Claim type="http://schemas.xmlsoap.org/ws/2005/05/identity/claims/test">VALUE!</Claim>
    </Claims>
  </StaticSyncSource>