There's probably a well-known indicator that chartists use to plot avg rate of change, but I 'm not a chartist and I don't remember anything from my cursory examination of the EL indicators that come with TS.
But rate of change is not difficult to code in EL, you just have to determine what it is exactly that you want to see.
You could do average rate of daily change over 5, 10, 20 days for instance.
Or you could do rate of change of the moving average or the weighted moving average etc.