I would like to have the ability to transform waveforms during audio playback. If I have this feature, it will be more convenient because you can work on it directly 
This is unlikely to happen because Audacity is a “what you see is what you get” type editor (also known as “destructive editing”). The entire architecture of Audacity is designed around modifying the audio data and displaying the data as it actually exists in the project.
There is another type of audio editing called “non-destructive” or “real-time processing”, which does not change the audio data until mix-down (or “exporting”). These types of editors apply effects during playback, but only to the audio stream that is playing - the actual audio data is not modified until mixdown. Examples of this kind of editor include: Reaper, Cubase, Sonar, Logic Pro, and many others.