First thing you need to do is extract the lua.scd file from your gamedata directory of Forged Alliance into a folder of your choice. Then create another empty folder named lua somewhere else. Subsequently copy the MarkerTemplates.lua file into that empty lua folder, then turn said lua folder into a zip file with no compression. This zip file must load after lua.scd so add a "Z_" to the start of whatever name you choose for your zip file. Then rename it to a .scd file (you may need to turn on showing of visible extensions in Explorer) and copy it to your vanilla Supreme Commander's gamedata folder. From there, when you start the map editor and load a map it will offer you all of the markers used by Forged Alliance.