Thanks for including your files to help with this.
What you’re seeing is expected Shift + Enter is not recognized or needed as a way to setup single space line break. Mac and Win should both recognize “only Enter” for single line break. You can use “Line Spacing” control in Property Inspector if you’d like different spacing.
Is there something you’re specifically looking for that you’re unable to do by selecting “only Enter”?
Adobe XDKamen Kirilov commented
As you see the problem is not the line Spacing but the New line breaks that are NOT recognized by Mac.
When some of the Designer create a xd file and someone open it from Mac the the file is completely broken because lack of new line breaks. New lines appear one line in MacKamen Kirilov shared this idea ·