Thankyou for using Microsoft Q&A platform and thanks for posting your query here.
As per my understanding you are trying to know if there is any way to add new criteria or condition to an existing alert rule in ADF. Please let me know if that is not the correct understanding.
You can go to Azure monitors and navigate to alerts>> Alert rules and then edit the alert rules and click on Add condition on top of the existing conditions and add the desired metrics and hit on save.
Hope it helps. Kindly accept the answer by clicking on Accept answer
button. Thankyou