A simple indicator code for learners which may also help you in manual backtest by just moving a vertical line to show hide bars.

Add the indicator to chart and Add a Vertical Line object with name "VL" and it will start working as soon as you drag the VL Vertical Line

You can move the line to left or right on chart and it will hide bars on right side

You can also press CTRL button to move bars 1 shift to the right for easy backtest