Hi Ufuk,
It is possible to apply event parameter-level filtering in the Firebase console using the steps below:
1. Go to the Firebase console and select the Analytics dashboard from the left-hand side navigation panel.
2. Scroll down to the Events card.
3. Click on "View Events" from the card.
4. On the "Events" page, click on the "Add Filter" button under the event name.
5. Configure and apply the desired filter
Note that there are also many more powerful reporting, data exploration and filtering tools available directly in the Google Analytics console. You can access it by clicking on the "View in Google Analytics" navigation link at the top right of the page when visiting the Analytics dashboard in the Firebase console.
Hope that helps!
-Sumit