The one big wish I have for an outliner is a horizontal view. This has been discussed at length in various posts on this forum. For example,

https://www.outlinersoftware.com/topics/viewt/9131/0/tree-app--macos

A recent application that comes close and maybe in development is Dashwood;

https://www.outlinersoftware.com/topics/viewt/9324/0/dashword

Is this the kind of feedback you after @Maurice Parker?