How do you open the long list of files in UltraEdit? By using the /f command line parameter with a list file or a different method?

From help of UE about command line parameters:

You may specify that the filename on the command line contains a list of files to open by using a "/f" parameter on the command line. In this case, UltraEdit will read each line of the files on the command line, and attempt to open each file. The file specified on the command line when the "/f" parameter is used must contain only filenames, and each filename must be on a separate line.

With that method it is not possible to prevent UltraEdit to get to foreground. When you do this multiple file load Windows Explorer starts for every file uedit32.exe with the file as parameter. It does not start uedit32.exe with all files at once on the command line. So if you have selected 20 files, Explorer starts 20 times uedit32.exe with 1 file. If you have not enabled Allow Multiple Instances every new instance of uedit32.exe called by Explorer detects that there is already an instance of UltraEdit, passes the file name to this already running instance via an event and terminates itself so only 1 instance remains. That event automatically brings the UltraEdit main window also to foreground and there is no option to turn that off.