I do not endorse this script, it was created at my request :)
Added new functionality to enable or disable each of the Standard Deviation bands, and to customize the number of standard deviations for each of the three. Current defaults are 1, 2, and 3 standard deviations, but can be changed.
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.