Display RSI for different / secondary stock ticker

There is no way to do this through any user settings. The only way to accomplish this in the current version of Thinkorswim is to create a new custom chart study with modifications to read from an alternate ticker symbol.

Here is the code for RSI based on an alternate ticker symbol:

declare lower;
input alternateTicker = "SPY";
input rsiLength = 14;
input rsiAverageType = AverageType.WILDERS;
input oversold = 70;
input overbought = 30;
def netChangeAverage = MovingAverage(rsiAverageType, close(alternateTicker) - close(alternateTicker)[1], rsiLength);
def totalChangeAverage = MovingAverage(rsiAverageType, AbsValue(close(alternateTicker) - close(alternateTicker)[1]), rsiLength);
def changeRatio = if totalChangeAverage != 0 then netChangeAverage / totalChangeAverage else 0;
plot rsi = 50 * (changeRatio + 1);
plot os = oversold;
os.SetDefaultColor(GetColor(8));
plot ob = overbought;
ob.SetDefaultColor(GetColor(8));