Create indicator from another Instrument/Candlastick

[FrancoisP]

Hello, I'd like to create an indicator. In a Renko candlestick chart, I'd like to import a trend indicator based on the 20-period EMA on a 30-minute timeframe.

Currently, I'm stuck on the import process in the Renko chart.
How do I create an indicator based on another instrument, or the same instrument on a different timeframe?
I considered aggregating the indicator in a sub-window, but since the candlesticks are different, I can't do that in this case.

I'm using the Claude AI for programming, but I'm stuck.
Here's the code the AI ​​suggests for importing the indicator, but I'm getting an error message:

Express FilterEMA30min

Vars
series ema30 (EMASource.ema);

Calculation
ema30 = ema30;

interpretation TriggerLine(ema30, ema30);

plot (ema30, "magenta", 2);

Error message:
Express 'FiltreEMA30min'
Line 4:
Unable to import the series 'emasource.ema'.

Thank you for your help.