MacJournal, like most apps, has a few hidden options that you can use. These are things that I think don't really fit into the overall design of the app, but might be useful for a limited few. The most notable is the option to show a new Preferences pane containing all the current hidden preferences. To show this, paste the following line into a new Terminal window:
defaults write com.DanSchimpf.MacJournal IncludeHiddenPreferences -bool YES
Then open up the Preferences window to see the new pane:
To remove the pane, replace the YES with a NO.
Note for version 2.6 and earlier: use IncludeHiddenPreferencesMenuItem instead.
Here's one that's not used in the user defaults, but rather in the Entry Template window. You can use "Entry->Insert Date and Time" to insert a tag that will be replaced with the current date and time when you create a new entry. It looks like <$DateAndTime$> after it is inserted. For some undocumented fun, try manually typing <$CurrentArtist$> and <$CurrentSong$>.
If you're a fan of the summary entry (see the AlwaysShowSummaryEntry hidden pref above), then you'll be glad to know that pressing Option-Shift-Command-S anywhere will show the summary entry for the current journal.
Keep in mind that one of the reasons that these are only accessible via the command line is that I'm not guarantying that these will work after this version. Some of them (like the date format specifiers) will hopefully make it into UI in the future. Others are conveniences for this version and might be removed in the future if they conflict with something else.