Threshold Rule : API has dynamic id in its signature

API signature has an argument {txn-id} in its URI, which gets value dynamically : : “GET /api/abx/granter/{txn-id}”

Appreciate your help on how to build the alert for this situation.
I'm using "Threshold Rule"

Which "Threshold" rule? There is the "Metric Threshold Rule", "Inventory Threshold Rule", "Log Threshold Rule", "Error Count Threshold", and "Index Threshold Rule".

Are you trying to set {txn-id} in one of the actions?

Pls refer to the case #00933935.

For that case, I'm told :
We are currently work to have filter for transaction name in the apm lantency threshold rule type but for now you can use this example to create transaction filters :

  • Click on “Metrics” under the “Observability” second in the left hand navigation
  • Click on “Settings” in the upper right hand corner of the screen
  • Add your apm index pattern to the “Metric indices” field.
  • Click on Alerts and Rules > Metrics > Create threshold rule in the upper right hand corner of the screen
  • Create an alert that looks like the following add the filter which might be "GET /transaction" and "service_name" :

Trying to use the above approach suggested by elastic and am stuck.
No I'm not setting the {txn-id}, just passing as is : : “GET /api/abx/granter/{txn-id}”