The Altiris Client Task Scheduling Agent is seen in the SMP Console under "Plug-in Versions" but is missing from the Sym Agent properties in the Agent Settings tab.
ITMS 8.x
There is a “Hidden” regkey under HKLM\SOFTWARE\Altiris\Altiris Agent\Plugin Objects\Agents\CTSchedulingAgent that configures if a plugin should be shown in SMA GUI. The default is "1" and when changing it to "0" it shows up in the Agent Settings tab.