This function was used internally in DTM to load script from a hosted location at runtime. It was considered an internal function, but proved too tempting to those who knew its power.
It does not exist externally in Launch.
The SDI Toolkit extension provides a way to expose Launch's internal loadScript module at runtime. To take advantage of this, Install the SDI Toolkit extension and on the Util Functions tab, check the box that says "Expose loadScript function from Launch Reactor."
Once done, the loadScript function can be accessed at
//Crusty old DTM way_satellite.loadScript('https://www.googletagmanager.com/gtag/js?id=ABC123');//Shiny new Launch way_sdiToolkit.reactor.loadScript('https://www.googletagmanager.com/gtag/js?id=ABC123');