Populating checkout fields

Topic summary

A developer has added a custom city dropdown to their Shopify Plus checkout page using checkout extensibility. They need help making the selected value from their custom dropdown populate the native Shopify city field.

Key Challenge:

  • Custom UI element created but not syncing with Shopify’s built-in checkout field
  • Seeking method to programmatically update the native city field based on custom dropdown selection

Status: Question remains unanswered with no solutions or responses provided yet.

Summarized with AI on October 31. AI used: claude-sonnet-4-5-20250929.

I added my own city dropdown to the checkout page using the extensively, any idea how I can make the changes to this dropdown reflect in the native shopify city field . That is populating the field .