Golden Cross within X days

You can run the scan multiple times with the existing code - just change the run date.

You can do that by clicking in the drop down above the scan window where it says Starting 0 days before... etc. Click on the zero, then click on any date on the calendar (any trading day). The scan will run looking at data as of the close of that date.

You can save the result in a separate list for each date, or merge the results into one list.

Also, I think to get a true golden cross, you should add code that says the 200 MA is falling (meaning, less than it was, say, a month ago).

and [sma(200,close) < 20 days ago sma(200,close)]

(note: the scan engine default is today and daily, so you don't have to specify that in your scan - ok if you do, but not required).