Text editor with blocks
Some newer text editor style apps (e.g. Notion) have a concepts called "blocks", semantic units within the document which are cool for e.g. moving things around on the page.
Something I'd be interested in exploring in the context of such an editor would be to have a kind of built-in block-level history, so you can e.g. start off with some bullet point notes, and then flesh out the text over various iterations, but keep them all saved as part of the history. UI-wise it could show multiple versions next to each other, or allow visualizing diffs between various snapshots.
Edited by Tobias Bernard