I use Notion.so. I have a page where I put all my thoughts no matter what they may be. Then I review it weekly to see what can be tackled next.

Unfortunately, Notion does not have a browser extension yet so you always have to open the website or app to jot down something, but I hope this will come soon.

If you want to add notes without opening an app, you can try Google Keep. It has a Chrome extension that works really well.