removes one level of column grouping from the specified range
| columnId | number|array | optional, a column ID or a range of column IDs [start, end] |
| page | string | optional, a page name |
$$("ssheet").removeColumnGroup();
If the columnId parameter isn't specified, the method removes a grouping level from the selected column(s).
Ungrouping doesn't work with multiple active zones (multiselect).