This script is an utility tool for manual backtesting. The main problem in backtesting a discretionary strategy is the bias of knowing the future result of the market, in this way all the market will be crushed into a flat line, this way you can avoid bias. The way to use this indicator is easy and made by 4 step:
Step 1 : add to an asset you won't backtest and put the auto scale on
Step 2 : go to the asset you will backtest and scroll left until the date you want to start
Step 3 : use the replay function of tradingview (15 min chart won't go back more than 18 month)
Step 4: toggle off the indicator or remove from the chart (untill next asset to backtest)
That's not a complex indicator but is what you need to do a fair backtesting