When I think of something I want to record quickly, and my computer isn’t at hand, I just record it as a text note or voice memo on my phone. (I have a dumbphone, but it still has voice memo capabilities.) I keep my phone by my bed when I sleep, and have Voice Memos set to a shortcut on the phone, so if I wake up with a thought, It’s really easy to record it. I haven’t actually re-listened to any of the ideas, since I know none of them are urgent, but just knowing that the thought is safely recorded and that I could theoretically continue working on it later is enough for me to relax and stop worrying about it. (I also back up the recordings to my computer occasionally for further peace of mind.)