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What you’ll learn: how a hierarchical (parent to child) picklist works, how its levels filter each other, and why the cascade wires itself once the levels are linked.What you’ll build: a two-level hierarchy (the linked Countries and Regions picklists) and two dropdown fields (Country, Region) where picking a country narrows the region list.Prerequisites: Part 4: Static picklists.

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Why this matters

“Region” depends on “country”: California is a US thing, Ontario is a Canadian thing, and nobody should ever see a form that lets them pick Ontario for the US. With two flat dropdowns and a hope that users read carefully, you end up with Country us and Region ontario in production and nothing catches it. A hierarchical picklist pushes that rule into the data model. Once a region option records which country it belongs to, the region dropdown filters itself the moment a country is picked, and the cascade is enforced for everyone.

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Concepts first

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Hierarchical picklist

A hierarchical picklist is a chain of Static picklists, one per level, built together in one editor. The first level holds the parent options (countries); the second level holds the child options (regions). When you save, each level becomes its own picklist, named after its column header and linked to the level above it. Each child option belongs to the parent option on its row. You can chain more than two levels, but the Campaign URL Builder sticks to two (Countries to Regions here, and the UTM hierarchy in Part 6).

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Cascading dropdowns

Two dropdown fields turn a hierarchy into a cascade: one field points at the parent picklist (Countries), the other at the child picklist (Regions). The child dropdown only offers options under the parent the user already chose. Pick us and the region dropdown shows California (and New York, if you add it). Pick ca and it shows Ontario. Until a country is picked, the region dropdown shows Select "country" first instead of options.

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The cascade wires itself

You do not manually tell the region field which field it depends on. When you point a dropdown at a child picklist, the field editor finds the dropdown that uses the parent picklist and wires the relationship for you. That is why you create Country first: until a dropdown uses the parent picklist, the editor shows “The picklist requires a parent dropdown to be created first.”

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Keep cascading dropdowns single-select

A flat Dropdown field can be single or multi-select. A cascade needs exactly one parent value at a time to decide which child options are valid, so leave Enable multi-select mode off on both Country and Region. Once Region depends on Country, the toggle on Country locks with “Not available when there are other fields that depend on this field.”

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Step-by-step

1

Create the Countries picklist

With the Marketing governance model open, click Picklists in the sidebar, then Create new, and choose Static Picklist. Click the Name column header, type Countries, and press Enter. This header names the first level’s picklist.
2

Add the country options

Add three rows: us / United States, ca / Canada, uk / United Kingdom. Enter the code in Code and the display text in Label, the same as Goals in Part 4. These are your parent options.
3

Add a second level for regions

Click + Level (the last column header; its tooltip reads Add level) to add a child level. The new level’s header reads Level 2. Click it, type Regions, and press Enter. Each row now holds one path: a country on the left and one of its regions on the right.
4

Add the region options under their countries

Fill in a region on each country’s row: california / California next to us, ontario / Ontario next to ca, england / England next to uk. To add a second region under a country, right-click that country’s row, choose Duplicate row, and change the copy’s region (for example new_york / New York under us). The copy lands right below, which keeps a country’s rows next to each other. Switch the toolbar from Flat to Grouped to see the regions nested under their countries.
A child code only has to be unique within its parent. You could legitimately have a north region under both us and uk, because they sit under different parents.
5

Save the picklist

Click Save. The editor saves two linked picklists, Countries and Regions, and both appear in the Picklists list.
6

Create the Country Dropdown field

Click Fields in the sidebar, then Create new, and pick Dropdown. Name: Country. In Picklist, select Countries. Click Save to draft. The Country field appears in the field list.
7

Create the Region Dropdown field

Click Create new again and pick Dropdown. Name: Region. In Picklist, select Regions. Click Save to draft. The editor wires the cascade to Country automatically.
📸 Screenshot coming soon: part 05 hierarchy editor

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Check your work

  • Two linked picklists exist: Countries with three countries (us, ca, uk) and Regions with at least one region under each country.
  • Two new fields exist: Country (Dropdown on Countries) and Region (Dropdown on Regions, cascading from Country).
  • The governance model has six fields total now: Campaign Name, Launch Date, Destination URL, Goal, Country, Region.

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What you just built

The first cascade. When a user opens a campaign form in Part 8, picking United States in the country dropdown filters the region dropdown to the regions under us; picking Canada filters it to Ontario. The stored values stay as codes (us, california), exactly what Part 7’s UTM Campaign field will splice together.

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Gotchas

  • Check the country code on every row. The parent sits on the same row as its region, so a typo like usa instead of us does not raise an error: it creates a fourth country, usa, with that region under it. Switch to Grouped before you save to spot strays. The editor does flag a region row with no country (“All parent levels must be filled”) and a country whose rows are split up by other countries.
  • Keep cascading dropdowns single-select. The cascade needs one parent value at a time. See the hierarchical picklists reference for the full rule set.
  • The cascade comes from the picklist’s structure, not a manual setting. Because Region points at a child picklist, the dependency on Country is wired for you. If you ever swap Region to a flat picklist, the cascade goes away.
  • Reworking the level structure of a live picklist is disruptive. Every child option is tied to its parent, so re-parenting options after records exist means remapping them. Treat the hierarchy as settled once campaigns are running.

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Next up

Part 6: The UTM cascade. Build the UTM hierarchy and meet per-taxonomy option filters (which Part 8 configures for real). For the standalone version of this cascade, see the cascading dropdowns recipe.