We have a process flow that creates items in a queue and allow users to fill in additional info. After the additional info is filled the user will mark the item as 'Definitive' via the task ‘Handle action’.
This triggers a process flow to send the item via e-mail. However we already have a process flow that processes mails (send_e_mail). The send_e_mail process flow must be run by Indicium Universal to have all the necessary rights to files and the SMTP server.
So we like to do a web request to Indicium Universal to start the send_e_mail process flow (see screenshot below).
Process flow that creates the queue item and calls the send_e_mail process flow via HTTP.

This all seems to be working.
The send_e_mail process flow looks in the queue for the most recent item and sends the e-mail. Because this doesn't guarantee the item to be sent is the item that is just created by the user, we would like to call the process flow API with the PK value of the created queue item.
I've tried to change the HTTP headers, the URL (https://[website]/indicium_universal/iam/[application_alias]/send_e_mail?pk1=1&pk2=100) and fill the Content but without result.
HTTP input

Are we missing something? Is this even a possibility when calling process flows?