Hi @francorzo,
Questions about the dnn_detect package should really be asked here: https://github.com/UbiquityRobotics/dnn_detect/issues/new
min_confidence is a parameter of the node. However, not all of the node’s parameters are exposed as arguments to the sample launch file. If you want to try different parameters, you should create your own launch file and add
<param name="min_confidence" value="0.7"/>
to the node. Hope this helps,
Jim