Hi Bart,
what's a multiline text string?
1) You have an array of string: simply use "string concatenate" to convert from array to scalar string.
2) Your string contains CR and/or NL characters: use "Search/Replace..." for this string, replace all EndOfLine chars by space (or which char you may prefer)...
Best regards,
GerdW

using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019