I'm new to Amibroker, have downloaded all US stocks data but just wondering how I can filter down to say s&P500 stocks only? In the symbols window it doesn't seem to have any indices data, but has data like sectors. Similarly I have ASX stocks data but doesn't seem to have indices data such as ASX300 etc.
For this kind of task, typically you'll import the watchlist from some text files that you create yourself or simply download (copy & paste, scrap, etc.) from some website (in many cases you'll need to edit the file to make a list usable by AmiBroker).
For instance, this site seems to have the ASX lists.
For the USA indexes, you can start looking at Barchart.