Have you ever checked an item and then noticed you "fat fingered" it and checked the wrong item. It would be cool to shake the phone to undo the last checked item.

please put carbonfin as a google doc open app

Add a view all outline button so you can have a quick overview of all outlines.

I would like to export all my OPML to disk for backup and searching purposes

At present when an outline is saved from Outliner Online, once reloaded frequently all nodes are in an expanded state. While they can be collapsed manually and that state seems to stick, using "collapse all" doesn't seem to stick at all.

On some of my outlines, I like to know how many children are below a given item. For example, a list of blog post ideas could be grouped under "Future", "Draft", and "Published" items. It would be nice to have the option to show how many children (but not grandchildren or great-grandchildren, etc..) are in each category.

I'd love any easy way to stamp (type) in the current date & time.

That and be able to see a per-item timestamp on an element in the outline. I suppose this would lead to having both a created and a modified timestamp.

But a quick timestamp macro would be great in the meantime.

The web version is too small and not practical to use on an Android phone. Can you either make an Android App or make a mobile version of the website that adjusts to the users device.
There are now more Android users in the world than iOS. Please take our money.

Mindmap / PDF / Markdown ...

An autosave feature

If you have more than a few outlines, you'll really need to group them into folders. CarbonFin Outliner doesn't currently support folders in Dropbox.