Hello BrianF,
"Shift+Enter" creates a new line in the text box in PLUS+1 GUIDE 2021.2.5.
This seems to be a bug. In PLUS+1 GUIDE 12.2 and 2021.1 it is only the "Enter" key, and I can't find anything in the release notes that this has been changed.
I will report this to the developer.
Thanks for letting us know.
Have a nice day.
NOTE: I saw that sverreo was faster than me.