Good question, though now I'm really out of my depth.

I know that some interjections and other particles have characters, very often with the "mouth" radical (e.g. 哈哈 "hā hā" = sound of laughing; 嘿 "hēi" = hey!).

How a Chinese would transcribe random growls or howls I have no idea.

As for "um" and "tut-tut/tsk tsk", I can imagine that there are conventional characters for those, but I have no idea what they might be.