# Select Field (Hierarchical)

_How to add and configure a Select Field (Hierarchical) in the {{Notebook}}
Editor._

---

## What This Field Does

A Select Field (Hierarchical) provides tree-structured navigation for
selecting values from nested vocabularies — such as pottery typologies,
biological taxonomies, geological classifications, or organisational
hierarchies. Users expand and collapse branches to navigate to their
selection, and the stored value can be either the full path
(e.g., "Ceramics > Coarseware > Cooking pot") or just the leaf node name.

> **Note:** This field is a **beta feature**. The hierarchy structure
> must be defined via JSON editing — the Notebook Editor does not yet
> provide a visual tree editor. Also consider the display
> size of the field on mobile devices.

## Adding the Field

To add this field, open the
[ADD A FIELD dialog](../shared-settings/adding-a-field.md), navigate to the **CHOICE**
tab, and click the **Select Field (Hierarchical)** card. Then click the
**ADD FIELD** button in the lower right.

> **Note:** The CHOICE tab may not be visible in the tab bar initially —
> click the **›** arrow button on the right side of the tab bar to scroll
> until it appears.

```{screenshot} field-types-design/hierarchical-select-01-add-field.png
:alt: Adding a Select Field (Hierarchical) — the CHOICE tab in the ADD A FIELD dialog
:align: right
:width: 100%
```

## Configuring the Field

Click the field's **grey header bar** to expand it and see its settings.
For an overview of the settings shared by all fields — including Label,
Helper Text, Field ID, and the field toolbar — see
[Field Identity](../shared-settings/field-identity.md) and
[Field Toolbar](../shared-settings/field-toolbar.md).

Give the field a meaningful Label, review the auto-populated
Field ID, and add any desired Helper Text.

```{screenshot} field-types-design/hierarchical-select-02-configured.png
:alt: Select Field (Hierarchical) configuration in the {{Notebook}} Editor
:align: right
```

### Select Field (Hierarchical)-Specific Settings

The Notebook Editor exposes only basic field properties for this field
type. The hierarchy structure itself must be defined by editing the
{{notebook}} JSON directly. A JSON editor is provided in the
Editor UI, pre-populated with a simple template. Expanding
the blue "Example Structure" info box displays an example of
a valid JSON structure with two levels.

| Setting        | What It Does                                                                                                                                                                                             |
| -------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Value type** | Controls what is stored when a selection is made: "full" stores the complete path (e.g., "Ceramics > Coarseware > Cooking pot"), while "child" stores only the selected node name (e.g., "Cooking pot"). |

The **hierarchy tree** (the `optiontree` structure) is not configurable
in the Notebook Editor and must be defined via JSON editing.

### Shared Field Options

Configure any of the shared field options as needed.

For settings shared across all field types — including Required,
Annotation, Uncertainty, Conditions, Copy value to new records,
and Display in child records — see
[Field Options](../shared-settings/field-options.md).

## Tips

- **Excellent for structured taxonomies** — pottery typologies,
  geological classifications, vegetation communities. The tree
  navigation feels natural for inherently hierarchical data.
- **Performance degrades above ~100 tree nodes.** For very large
  taxonomies, consider splitting into cascading Select Field dropdowns
  instead (e.g., one for material, one for technique, one for form).
- **Once a selection is made, it cannot be cleared** — there is no
  deselect mechanism. If users might need to undo a selection,
  include a top-level "-- None --" node in the hierarchy.