In a situation of pikuach nefesh (for one Jew or many Jews or even for a non Jew or many non Jews), if one knows how to utilize Kabbalah Masseios (Practical Kabbalah - Using Divine names for "powers") - can he? To save the person(s) from death? Or is that changing GDs plan (why is that different than praying)?
There are countless stories of Sages in every age doing such things including in the current day. It is not the common practice and is prohibited for almost everyone to indulge in such activity for a variety of reasons.
One textual example that comes to mind of this type of teaching is Sefer Ta'alumot Chochmah by Rabbi Chaim Vital which actually categorizes according those methods tried and tested and those only heard of, as well as their efficacy.
There is also the famous amulet of Rabbi Mordechai Sharabi, zt"l which was used by Rav Kaduri, zt"l and Rabbi Mordechai Eliyahu, zt"l. This link actually connects to a photo of one of the notebooks from Rav Kaduri, zt"l about writing amulets that was placed up for auction in 2018.