Here is an exploration code to filter out tickers that do not have enough data for your backtests.
SetBarsRequired( sbrAll, sbrAll );
Filter = BarCount >= 1000; // Only show tickers with at least 1000 points of data
AddColumn(BarCount,"BarTotal",1.);
SetSortColumns( -3 ) ; // Sorts Ticker file size in decending order
Set the range to "1 recent bar" in the Automatic Analyser, and most importantly, uncheck the "pad and align" checkbox in settings.
The tickers will be sorted with the largest data tickers on top. To save in a watch list, select any ticker and right click on it for the menu to save your search. The tickers will be saved in the sorted order.
Having the tickers sorted in the watch list by data size is important when doing backtests on this watch list as Amibroker will limit the date range to the first ticker it encounters.