I found this tweet via https://iwishtherewas.app/, a Twitter crawler for app ideas:

Is there an app that lets you type a quick text note and then hit add, to save the date and time and note as a line in a spreadsheet? For tracking animal visits or meteors or whatever?

So I made a simple Svelte + Tailwind.css app to do just this. It allows you to customize form fields, saves entries to local storage, displays in a table, and exports to CSV.