Without a sample workflow or more details about what you’re trying to achieve—and the errors you’re encountering—it’s a bit difficult to provide specific help.
Could you share a sample of your current workflow and maybe a small snippet of the data you’re working with? That would help a lot!
Okay, I think the trick is in the Merge node.
You need to use it in Combine mode, set the matching fields, and enable Fields to Match Have Different Names
Then, enter your fields (id, parent_id)
Because we are referring to the input field name directly, we didn’t use an expression,
However, if you want to use an expression, you can use {{ $json.id }} and {{ $json.parent_id }}