LicenseFile specification with several guixt.ini files: We have a local guixt.ini file in which we use "SwitchTo" for a second guixt.ini. In this guixt.ini we again use a "SwitchTo" leading to the final guixt.ini. Where should we put the "LicenseFile" command?

Technically you may put it in any of these guixt.ini files, but check that it comes before the SwitchTo command, otherwise it is ignored. In most cases the best place will be the final guixt.ini where you have all the other configuration parameters.