Thank you for the kind words :)
Sadly there's no built-in way to save your entries. This was on my to-do list but never got around to it. However, if you open the savegame file your text should be there. Formatting might be a bit weird though. You can also delete these files if you want to reset your progress.
You can find the save files here:
C:\Users\USERNAME\AppData\LocalLow\DieHappy\Scribble
The file with your text in it is called:
journal-challenges.data