The way you would like it, the answer is "no". Currently, the only way to create a magic word is via slimLAUNCH and Alt-Enter. It wouldn't be difficult for me to add such an option. The only problem I see is that a slimLAUNCH hotkey is bound to its sources, a list of monitored paths. These paths can be a single filename. This means I could add a hotkey for specifying custom filenames and commands (the magic word) that would get added to the source explicitly. For the moment, what you can do is add a new FileSystem source to your slimLAUNCH hotkey, select a "user-specified path", enter the file's path in the "path" field and the file's name in the "restricting file masks" field, making sure to uncheck the "also look in subfolders" option. Then you have to do the Alt-Enter trick the first time.
This is painful, but should do the job until I add such a feature.
Thanks for the hint!