While the free form of notes is useful, there are also scenarios where I'd like to feed/store handle structured data in my Brain (like records of database).
So the parent thought could have some flag associated with it that would cause all child notes to have a certain type.
And for every type, it should be possible to add "fields" to notes (in addition to a "text" field that all notes have). Field types could be (in addition to "markdown") be "integer", "float", "date", "boolean".
And these fields should be available in selections with comparison options as appropriate for the fieldtype.
etc etc... ;)