When you load up HL7 Soup you are presented with a selection of example HL7 messages. They are great to get you going, but won't necessarily be what you normally need at start-up.
You may want your own message samples, or maybe you just want a blank page. The great thing is that you can change these by simply making your changes and clicking save.
You can add your own HL7 messages, delete the ones you don't like, or edit the defaults to your hearts content. Just click save when you are done, and you'll be confronted with your changes when you next load HL7 Soup.
So where is this stored? Well, I did a bit of hunting and found the file is stored at
%appdata%\hl7soup\Sample HL7 Messages.txt
You can just put your own file in its place too and it will be picked up as the HL7 Soup default.
One last thing, you might want to revert to the HL7 Soup default messages again. I found a simple workaround that recovers these. Just delete the file I mentioned above and when you reload HL7 Soup it will add it back in with the original sample HL7 messages. Very handy.