@Didymos Thomas,
I'm merely 19. I imagine the bulk of our members are older than myself.
But I'm not sure why a dictionary is useful if the concern is others appreciating what you write on those blank pages. Context is a wonderful guide to meaning when meaning is otherwise unknown to the reader. Also, as I said, a quick explanation of some invented term would do no harm to the value of your text. Aldous Huxley did not suffer for inventing words.
Honestly, I think inventing words to express some meaning you have in mind would be superior to adapting some other term that closely resembles the meaning you have in mind. Learning a name for something means we learn how to distinguish between X and non-X. We do not understand "cat" if we call a spider a cat. Thus, we learn X and not-X as a single, socially shared way to make a distinction. You're on a deserted island, not a metropolis. What need have you of socially imposed meanings?
Of course, this presupposes a general familiarity with whatever language you use. If, for example, someone is unfamiliar with grammar, a dictionary might be invaluable. But if we understand syntax, we can use whatever terminology we please, even if the terminology is invented.
Inventing all of this might even be a blessing - we are alone for the next decade on this island.