Why isn't a new Typed Property or Operation - which has Public as default access modifier - marked as public with the green + ?
The + isn't displayed until you switch the Visibility from public (default) to private and then back to public again.

This is a bug. I add a new issue in the bug tracker : https://github.com/ObeoNetwork/UML-Designer/issues/909
The issue will be fixed for the next version 7.2 of UML Designer.
An equivalent bug was already fixed for the property creation tool but the bug still exists for the typed property creation tool.
Thanks for your feedback!