Such as,
SMA(RSI(close,14),7),
StandardDeviation(EMA(price,12),24)
Status changed from Archived to Refused
It would mean a very big change to the code, it doesn't work on all platforms and I haven't seen any indication that this features produces better strategies.
Look at Hull averages as an example. It uses nested functions and is a very effective indicator. It was eventually added directly by the Dev team but it could have easily been added by any user much earlier if nested indictor functionality was available.