Replace this heading’s title with new_title. Only for heading blocks (HEADING_1..6). depth is number of '#' (1–6). and title. Note: only level and children are updated; kind is unchanged, so kind can be inconsistent with level (e.g. kind remains HEADING_2 while level is 5).
| depth |
number of '#' (1–6) |
| new_title |
heading line text |