I used to try and do exactly this. I kept a pen and paper on the nightstand and if an idea came while I was starting to go to sleep, or during sleep while dreaming, or just as I was in that nether region of almost awake but not quite, I would write it down.

And THAT is what I would see in the full consciousness of the next day. Sometimes not even as legible as this, but still with no idea WHAT I meant when I wrote it.

Now I just write things down in a notebook I carry when I’m awake and fully conscious.

And there are STILL times I have no idea what I wrote or what it meant, lol!