I'm pretty sure we should never use &TRACKINGKEY& directly into the reporting. It looks better to use a variables like this:

For not multi instance
<pre>
"rudder_mytechnique_uuid" string => "&TRACKINGKEY&"
</pre>
For multi instance:
<pre>
&TRACKINGKEY:{uuid |"rudder_mytechnique_uuid[&i&]" string => "&uuid&";
</pre>