I'm not sure I understand your questions.
Highs and lows are not absolute, they are always relative to something. If you were trying to find a relative high for an oscillator you could create 2 condition blocks where the first checks to see if the RSI 2 candles ago was less than 1 candle ago, and then another condition to check if the RSI 1 candle ago was was greater than at the current candle. That would detect a relative high in the RSI I think.
Currently with Fxdreema you need to import a custom indicator if you want one indicator to use another indicator's data. I haven't looked into how to do this. My coding abilities in MT5 are almost non-existent.