@mvgalindez,
There is a limitation in Fluid Checkout regarding adding new fields, where the fields added to the shipping or billing section that does not have a correspondence in the other section will be displayed after the common fields.
For example, if you have custom fields for “Start date” and “End date” for an insurance policy added to the billing section, these fields will be displayed after the common billing address fields regardless of the order (priority) set for those fields via a checkout fields customization plugin or code snippet. However, if you add the corresponding fields to the shipping section, the fields will be displayed in the correct order as defined for both the billing and shipping sections.
Corresponding fields are fields that have the same ending on their field keys, for instance:
billing_address_1 -> shipping_address_1
billing_start_date -> shipping_start_date
billing_end_date -> shipping_end_date
Although not ideal, this limitation is what makes it possible to use the option “(billing) same as shipping address” with a decent user experience.
We have a task on our back to try to improve this in the future.
More information about checkout field customizations can be found in the article below:
https://support.fluidcheckout.com/portal/en/kb/articles/customize-checkout-fields
Best,
Diego
