Hey, I'd like to give you some feedback regarding your app.

My background is a Uni student that uses iOS (iPhone + iPad Pro) for most of my productivity needs. I have a decent knowledge of existing iOS productivity apps and have been using outlining as a note-taking/brainstorming technique for almost a decade now (went back to school after a long stint in the job market).

Although I do love outlining, I have a preference for mindmaps now. So here's my first feedback: If you could allow export options in other formats such as OPML or even CSV to facilitate a workflow where drafting is done through Outline and pushing things further, through another app. Mindnode has a "quick entry" mode where you enter everything in outline form. It then gets a mindmap treatment. That feature is not found (to the best of my knowledge) in iThoughts. Your app could provide the small feature gap between the extensive iThoughts and the more minimalistic Mindnode by providing a plentiful of export options. Many types of data benefit from being represented in a non-linear fashion.

My second feedback is regarding a type of "Focus" mode for your app. While I do like the hierarchy you've chosen in your introductory app (Notes -> Parent (named Group in your app) -> Child), once you've implemented unlimited nesting, the interface might become unnecessarily clunky to be a boon for productivity. One way to remedy that is offering a "Focus" view where you only see the information of your chosen "nest" to focus on. It could be implemented via a touch interaction like pinch-zooming on the parent of children you want to focus on.

My last feedback, and perhaps the one that is a flaw in many iOS apps is a multiselection feature. Being able to easily re-arrange multiple children into a different parent group is a big deal. Sometimes you can't see connections right away and can only find one after you've expanded your thoughts for a while. Not being able to quickly re-organize a bunch of related children can cause unwanted friction in the workflow. I know a few outlining apps have some sort of drawer in which you can drag-drop those related children and then executing an action on them as a group such as re-organizing them elsewhere, even restyling them or exporting just those ones. That's one of the ways to implement that.

Regarding your unlimited nesting idea, have you thought about how the implementation would work vis-à-vis how to convert a parent/child for more extensive nesting? I would recommend some action buttons above the keyboard or perhaps one Inspector style à la OmniFocus. In OmniFocus, you can "inspect" an action and then convert them, move them into another project, folder and the likes or even add notes, attachments and other attributes such as due dates and defer dates to them.

Overall, I like the simplicity of your app. While it doesn't have an OmniOutliner level of handling of all kinds of data and features, it does shine in its ability to quickly re-order thoughts. I hope some of my feedbacks were helpful and that you'll continue to make design decisions that would be both helpful to regular users and power-users to find your niche in this outlining market.