Chabad starts the Half-Kaddish by Mincha Shabbos afternoon just after Hagbahah and continuing the Kaddish until the Sefer Torah is put back in the Aron.
Since one should not interrupt in the middle of the Kaddish, When does one say "Yehallelu"?
According to Siddur Rabbeinu Hazakein, the Lubavitcher Rebbe would wait until after Kaddish was over, right before Shemoneh Esrei. However during the years תש״נ ־ תנש״א / 1990 - 1991 Kaddish would not start until after the Sefer Torah was already put back in the Aron, so yehalelu was said before kaddish.
As regards actual practice, every Lubavitcher minyan I've ever been in waits until after kaddish, and says yehalelu right before shemoneh esrei.