Reminds me of Scrivener, which I used for years. I use OneNote now. OneNote is so much better and integrates nicely with Windows. Curio looks a lot like Scrivener.
Scrivener, OneNote and Curio have different primary use cases.
I understand that. I journal and do my own research and I try to write other stuff sometimes. I am looking for a piece of software to organize my findings, thoughts, and capture my writing and other things. They can all be used off of their main purpose, and I have found it helpful. I like OneNote's mixed media in notebook style, but then again, I was in love with Mathematica's notebook format (long before Jupyter and the rest) many years ago. I will have to evaluate Curio further, but at the end of the day, sometimes my pen and journal are my all time favorite for stream of consciousness with some forethought to the writing being "permanent" and not so easily 'backspaced', 'deleted', or 'spell-checked' or 'grammar checked', and best of all, no popups!
Scrivener came to mind for me as well. I've adopted Emacs' org-mode as my Linux-friendly Scrivener replacement and I like it a lot.
OneNote is pretty nice and was my go-to app on iPad for infinite whiteboard notes until I discovered ZoomNotes, the other app Curio made me think of.