Some sort of 'legend' or Notes area so that I can add notes about things that apply to many entries.
In old written diaries I sometimes make reference to people - but now I've forgotten who they are. If I had made a note at the start of the diary of who they were or what initials stood for, then I'd know be reminded of who they were. Or I might use a code to describe how say films are - R for rubbish, never recommend this to anyone, R+ for rubbish but you could imagine other people liking it so don't put people off going to see it. R* for rubbish but had elements that you liked. That's not a great example, but would just like a Notes area for things that might apply to many diary entries. (What would be really brilliant would be if you could click on a link (someone's name say) and it would take you to the Notes entry which explains who they are - but I appreciate that might be too much to ask)
In the meantime I might set up an entry (in say 9/9/99) that contains Notes.