It uses a method and provides code that:
— Allows the indicator's users to select the plotting of markers representing the different conditions used to trigger alerts.
— Allows filtering of the markers on direction: both, longs only, shorts only.
— Uses a single alert for the indicator. It will trigger on any number of marker conditions selected by the user when the alert is configured. The user can thus create the combination that suits his needs.
— Includes the marker's number in the alert's message.
— Alerts should usually be configured to trigger Once Per Bar Close to prevent false signals.
— See the Pine User Manual page on alerts.
— This code uses the Pine Script Coding Conventions.
In true TradingView spirit, the author of this script has published it open-source, so traders can understand and verify it. Cheers to the author! You may use it for free, but reuse of this code in a publication is governed by House Rules. You can favorite it to use it on a chart.
Copy the whole snippet in your editor and you'll see the special character used to lift the lines up.