How to block specific notifications from an app?

If your Android is rooted and has Xposed Framework installed, then NotifyClean xposed module can be used to easily achieve the goal. I have mentioned its relevant usage here.

For non-rooted Android devices, I suggest you use MacroDroid or a similar app, such as Automate.

MacroDroid defines a set of trigger(s), action(s) and constraint(s) as a macro. You must enable Notification access permission and Usage Access permission in it.

You would be needing the following macro.

• Trigger: Notification → Notification Received:

  
  
  
  
  
  • From: choose your app
  
  
  • Text Content: here's where you can play. Choose Contains or Matches to filter your text specific notification.
  
  



• Action:

  
  
  
  
  
  • Clear Notifications → Select Application(s) → select your app → provide the filtering details again
  
  


• Constraints: none

Save the macro and you're good to go.

Note: MacroDroid can remove sticky/persistent notifications only in Android Oreo and above.