This is a new thread devoted to this topic. I originally posted about this in the following thread here:
The request is to allow a method for automatic outline numbering (especially for project schedules) as one of the options within the Autonumber data type, or as its own data type.
Option 1: 1, 1.1, 1.2, 1.2.1, 1.2.2, 2, 2.1, etc.
Option 2: Capital Roman Numerals > Capital Letters > Arabic Numbers > Lowercase Letters
Option 3: 1., 1.a., 1.a.i., 1.a.i.1., etc.
The primary reason for automated WBS numbering is to avoid the annoyance of having to manually update your outline numbering when you insert or delete a task. There may be other reasons to use outlining in spreadsheets, but work breakdown structures are surely the most common use case.
It’s important that this data type be allowed as one of the selectable columns for the Predecessors column in the Gantt view. This allows the Predecessors column to be narrow (as opposed to choosing the task title as the predecessor).
Indenting would be how you modify the level of the outline.
When using complex formulas to generate the automatic numbering (until you develop a sibling function), there are issues if you try to use a sort action because the OFFSET function changes the numbering based on the new sort. However, because sorts don’t permanently change the original row order (unlike Excel or GS), you can turn off the sort to return the numbering back to normal. Most of the time, you’ll want your Gantt view to display the tasks in their proper hierarchical order, so sorting is not as commonly used. But the point is that the effect of sorting and filtering may need to be considered when implementing the automatic outline numbering. There may also be a case where a person intentionally wants to reorder all the tasks so that all the outline numbering updates based on the new sort (though again, this is less common if they are intentionally creating a work breakdown structure). It may be sufficient to ignore the effect of sorting and just say that sorting is not supported when using an Outline data type.