AppTree and SCCM Task sequence

I have some Problems to get that running… 


First, I have configured the Software part:

<Software>

<Application Id="00000001" Label="Citrix Receiver (FM)" Name="Citrix Receiver Enterprise"/>

<Application Id="00000002" Label="Adobe Acrobat PRO" Name="Adobe Acrobat 2017"/>

<Application Id="00000003" Label="DIALux" Name="DIALux evo"/>

<Application Id="00000004" Label="FileZilla Client" Name="FileZilla Client"/>

<Application Id="00000005" Label="FormsForWeb Filler" Name="FormsForWeb Filler"/>  
</Software>


then the AppTree part:


<Action Type="AppTree" Size="Regular" Title="Choose Software">

<SoftwareSets>

    <Set Name="IT">

        <SoftwareGroup Id="Group1" Label="Default" Required="True">

            <SoftwareRef Id="00000001" />

            <SoftwareRef Id="00000002" />

            <SoftwareRef Id="00000003" />

            </SoftwareGroup>

        <SoftwareGroup Id="Group2" Label="Additional">

            <SoftwareRef Id="00000004" /> 
            <SoftwareRef Id="00000005" />
        </SoftwareGroup>
    </Set>
</SoftwareSets>

So far, so good… My expectation was that within the Tasksequence I can install the choosen Software using the %XApplications% variable... but that does not work. Do I have to add the TSVarList Action Type? Or am I missing something else?