Another application I use is called “To Do List”. It’s free software. It allows you to organize tasks into a tree-hierarchy. I use it to keep track of a lot of my ideas, which I organize into subcategories. I’ve also used it to keep track of bugs reported by users, or maintain a list of things I need to do. Here’s what it looks like:
You’ll want to remove the columns you aren’t using, otherwise the interface gets cluttered with useless information. You can also write extra information into the right sidebar, including being able to copy-and-paste images into the sidebar. You can also attach a file to each item in the list.
You can get ToDoList here.