How to report parameters in Firebase Analytics Events

I've used Fabric with iOS before where it was so easy to report custom parameters in the same analytics event in like this:

Answers.logCustomEvent(withName: "saved_border", customAttributes: ["image_index":"\(index)"])

Now I'm trying to do the same with Firebase Events but I see only event names in console (without custom parameters) Here my code:

Analytics.logEvent("saved_border",parameters: ["saved_image": index])

Is there any way creating same with Firebase except appending index to event name?

Now this is done using Custom Definitions in Firebase, according to this doc: https://support.google.com/analytics/answer/10075209

You need to go to Firebase Console and define Custom Definitions

After that and after you wait for 24hrs in Google Analytics you should be able to see this custom dimension with your custom event and custom parameters