When saving a value in a dot-walked list type field. The value does not save in the list type field when the record is updated.
List type fields cannot be dot-walked
Instead of using a list type field. Use a reference type, as dot-walking is allowed.
Steps to reproduce:
1. Create a list type field on the task table
2. Navigate to the "idea" table (Requires Project Portfolio Suite with Financials plugin)
3. Configure the form layout of a Idea record.
Under "available" find "parent" and expand this field. Add your custom list type field you created on the task table.
4. Save the form layout and add a value in your list type field
5. Notice that the value is not stored in the list type field.