Is there a way to hide text following an @ sign for multiple lines?

You can do this natively:


Here is the formula I used:

var Text parta = Part([text], 1, "\n");
var Text partb = Part([text], 2, "\n");
var Text partc = Part([text], 3, "\n");
var Text partd = Part([text], 4, "\n");
var Text parte = Part([text], 5, "\n");  
List("\n", 
  Left($parta, "@"), 
  Left($partb, "@"),
  Left($partc, "@"),
  Left($partd, "@"),
  Left($parte, "@")

)

There might be issues in the future using this formula as errant characters might get pasted into the [text] field that mess up the formula. Even this simple formula is reaching the edge of what can be done naively. Parsing is better done with JavaScript at the time of data entry.

The parsing capabilities in JavaScript will blow your mind and are only getting more awesome over time. I myself am looking forward to the look behind feature coming out in the upcoming JavaScript standard:

ES2018: RegExp Lookbehind Assertions
http://2ality.com/2017/05/regexp-lookbehind-assertions.html