Workflows commonly use the data copier automation step to transfer data, including custom subforms, so one workflow instance can update another automatically. When subforms are shared between parent and child workflows, the data copier replaces all matching fields and entire subforms, rather than merging them.

This article explains this behaviour, its rationale, and important points to consider when designing workflows that share subform data.

1. Processing subforms

When data copier runs, it follows a specific process for handling shared fields and subforms:

1. It looks for matching shared fields between workflow instances.
2. If a subform is shared, the copier copies the entire subform block.
3. All rows and all subfields - whether filled or blank - are written into the target workflow.
4. Existing subform data in the target workflow is fully replaced.

This behavior is expected and applies across all workflow relationships, including:

• Parent → Child
• Child → Parent
• Sibling workflows within a workflow family

Data copier doesn't skip overwriting fields when the source is blank. It copies all values, including blanks.

Example
A parent workflow contains subform Columns 1-5. A child workflow only fills Column 6.

When the data copier in the child sends data back:

• Columns 1-5 from the parent are overwritten with blanks (because the child workflow has no data in those columns)
• Column 6 is populated from the child workflow

2. Working with shared subforms

If you use shared subforms across parent and child workflows, consider the following approaches:

• Use separate subforms - Keep parent-only and child-only data in different subforms to avoid overwrite conflicts.
• Only copy data in one direction - Avoid bi-directional subform sharing unless the data flow is strictly controlled.
• Avoid partial subform completion in the parent - If the parent workflow must begin populating the subform first, ensure child workflows do not trigger data copier before the parent is fully complete.
• Use additional fields instead of subform columns - If only one or two child-only values are needed, using a standalone shared field may be safer.