LogCat is missing the filters options
There is a way to make it appear. Just click the "Event log" label in the bottom-right of AS.
But it may will miss again in some case... I guess whether it's a bug of AS.
This bug is still existing in Android Studio 3.5 the lastest stable version, I got it just now(08/26/2019 3:13PM).
Had this problem on Android Studio 3.2 Beta 4 (Windows 64-bit). Toggling 'Floating Mode' on and off again made the filters reappear. Bit faster than exiting Android Studio if you're lucky enough.