Ok, I've tried multiple methods to do this and so far, no success.
If I manually set the contents of a text.text to "This" & newline & "That" It properly displays: This on one line and That on a second line.
If I try to set the text.text from a JSON.Get("MyKey") to "This" & newline & "That" I get: "This" & newline & "That"
I have tried various combinations of removing quotes, adding quotes, etc. Whatever I do, it doesn't seem to be parsing the text field properly and adding in the newline.
Ok, this was not what I expected as the answer but it works:
I was creating a JSON in PHP and sending it back to C3 with an Ajax request and having C3 fill in the text field with the JSON value. I stupidly assumed that if I sent the text as C3 expected to find it that it would parse it and add in the newlines. It appears it does not. This solution seems to bypass the need for Construct to parse the line and properly adds in newlines.
$jsonObject->Error = '"This" & newline & "That"'; // does not work
$jsonObject->Error = "This\r\nThat"; //does work