Thanks @Steven Boardman
So what I've done is set the field ID for the question to h_custom_a_custom_o
Then, on the 2nd automated task to Update Request ID I've picked the variable Custom field A, so &[global["flowcode"]["customFieldA"]]
Once I Validate, I see the warning That nodes have invalid variable references.
Oh, I did test too but it didn't populate the External Ref field