I want to apply Audio Waveform Filter, but I have a problem: I can't drag an audio to the video timeline, only to the audio timeline, so I can aplly the effect but I can't to see waveform.

I have 19.08.1 version.

Can someone help me?

In older versions drag audio in the video timeline can be done, and thus be able to use the effects like the next video
https://www.youtube.com/watch?v=BvdedWMt5mU

Hi, you have to fill an ISSUE report about that, maybe linking the video just to make sure developers can understand the "malfunction"

https://invent.kde.org/kde/kdenlive/issues ( NEW ISSUE button )

This can be done using the master effect. Click on Master on top of all tracks -> and drag/drop the "audio waveform filter" into the master effect window.