In order to make some tests and not add unwanted extensions to my usual tce dir; when the system was running I changed the contents of /opt/.tce_dir to /tmp/tce .
Using the ab command I choosed qmmp-ProjectM.tcz ondemand, I've seen that the extensions I've already installed are downloaded, For example Xorg.
Xorg it's true is not in /tmp/tce/option but it's installed.