Disabling Word-Wrap in XCode
I think that you are searching for the checkbox under Preferences>Text editing>Indentation>Wrap lines to editor width.
Main Menu > Xcode > Preferences..., select Text Editing tab. Select Indentation sub tab. Uncheck Line Wrapping.
This is moved (at least as of) Xcode 12.4:
Xcode > Preferences > Text Editing > Display > Wrap lines to editor width