This was a bug in Objo Studio rather than a problem with Picture.
When a property was moved or pasted from a Window, Class, or Container into a Module, Studio changed Property to Var but incorrectly retained its scope modifier. This generated invalid source. The compiler then reported “Expected declaration after modifier.”
Studio has now been fixed to generate the correct Module declarations. The fix will be included in the next release: https://feedback.objo.dev/bug/1230
Until then, deleting and recreating the properties directly inside the Module will avoid the problem.