wen will the audio support for animation be back?

It is listed as removed, but oddly, you can still load mp3 files to your project, and Krita will play back these (at least with the latest, 4.1.5 release).

One thing would be really helpful if we could actually see the waveform of the audio.

The audio for animation is/was buggy and had several issues. Afaik it is fixed now (at least one of the reasons it didn't work is fixed), but the fix is not in an official release yet; I don't know if it will appear in 4.1.6/7 or in 4.2.0, but it will eventually. It is already in the nightly versions of Krita, but they can have other bugs so it might be a better idea to wait for the official release (although it's great if people use the nightly or alpha versions and report issues, that way developers know what to fix before it makes its way to an official release; usually when bugs are not fixed in the release version it's because nobody noticed them before, because not a lot of people used them).

(Disclaimer: I'm not a developer)