This indicator helps in letting the trader focus on a particular date/candle across many symbols.
Tradingview currently has a bug in Bar Replay - when we switch symbols, the bar replay resets.
Hence if you are backtesting & running through a bunch of symbols, it is nearly impossible to focus on a particular historical candle across all symbols.
This indicator plots a vertical line on a given bar_index which remains as it is while you are switching symbols.