How can I pre-register my study of little importance?
If you have the time for it, you could blog the entire process from initial idea through the final writing of the paper. A public blog might not be the same as a, audit but the public nature of it would provide assurance. A research notebook open to the public, so to speak.

But I suggest this since a blog of a research "journey", including all attempts and all setbacks would be, perhaps, useful for others starting out in research. The fact that, you say, it isn't very deep might be an advantage, making it more accessible to readers. 

It might even make you a better writer; valuable in itself. 

There are a lot of blogging platforms, of course. And I realize this isn't exactly what you were asking for.