It is currently not possible to do this. You must specify players individually. However, you can work around this by adding as many "fake" players as you need and setting a few preferences.
- Add as many players as will be playing to the tournament, and just give each player a number for a name. An easy way to do this is to import players from a CSV file, where your CSV file is just a list of numbers, one on each line. See attachement for an example of 100.
- Turn off automatic table balancing suggestions (Tables tab -> Settings button)
- Turn off "Display unbalance tables icon" (Preferences tab)
- Turn off "Allow selection of hitman when busting players out" (Preferences tab)
Now you have 100 (or however many you need) "generic" players in your tournament. The software won't bug you to seat players or move them. When you buy players in, purchase rebuys, bust players out, you just select any player in the list. The software won't care about a hitman when you bust a player out.