I've also done the untitled tabs in Sublime thing.

Workflowy (https://workflowy.com) is worth a try.

It's still very lightweight. You have one doc which has one master root. Then, you can create arbitrarily nested lists of things and zoom in and out of the overall list. You get a daily email of your delta from the day before. There's an okay mobile client but the desktop one is much better feature wise.

I've been using for it everything from an inbox to blog post ideas lately (I just start drafting the post inside Workflowy).