Current Trading View free plan allows only ONE active alert.
This simple indicator Allows to trigger this ONE and ONLY alert when price reaches Higher, or Lower price level.
You can set levels and turn alerts for them on/off in settings, or by just drag-n-dropping Horizontal lines on the chart.
To set the only alert you need to create new alert, and change it's following parameters :
condition : 2alerts
Any alert function() call
Feel free to modify it on your needs.