I'm thinking of an alternative to Scrivener for Window's "Split with
selection as title (Ctrl+Shift+K).

So, you highlight some text, and Scrivener splits the text just before the highlight, and assigns the selected text as a title for the text following the split? Just want to make sure I understand.

In answer to your question, you know that I am going to recommend Ecco! haha. It's great for moving text around, and you could export tab delimited text where it needs to go. But it's not dual pane (in the sense of item titles in a tree pane, and item text in another pane).