Recommended and mentioned products
A second brain, for you, forever. Obsidian is a powerful knowledge base that works on top of a local folder of plain text Markdown files.
Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
freemium $12.5 / Monthly (Per user - Business Class)
If you're not hellbent on it being a windows app, I use Trello for organizing thoughts. Create an entire workspace for a single project, then loosely related ideas on their own boards.
The Markdown-based note-taking app that doesn't suck.
Notable is very sleek, has both a light and a dark mode, and it allows for Markdown formatting and multiple note sheets if you want to give your thoughts some structure.