In my head I don't really relate transmute strongly to mutate though the documentation strongly links them. I just see transmute as the only tool that gives me full(ish) flexibility in defining the columns I want in my tibble in whichever order I like and which can include transformed columns or constants if I want.
When I do use it, I tend to put one column on each row of the code to make it reasonably easy to read and I only use it when my transforms are very succinct ones (maybe calls out to transform functions I have written).