Hello.
There should be a field with the type "Contact Directory" - you have it
https://prnt.sc/wi4v9jIt should be understood that there will be no drop-down list here, you will have to write at least a few characters anyway.
Further, the simplest way is to set the action "Change invalid", select the field that you created in it, and check the box "Change the responsible subprocess" below and select which subprocesses to change the responsible one for, for example
https://prnt.sc/wi4x67