A DESCRIPTION OF THE REQUEST :
isVisible is defined in javafx.scene.Node which a good many objects extend except for javafx.stage.Stage and thus javafx.stage.Window which javafx.stage.Stage extends. javafx.stage.Window should also implement isVisible.

JUSTIFICATION :
javafx.stage.Window should implement isVisible to simplify the model used for simplicity and consistency across models.


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Expect visibility to be handled similarly for Stage and Window as well as other objects that implement Node.
ACTUAL -
Visibility of Stage and Window are handled differently than that of other Objects that implement Node.

---------- BEGIN SOURCE ----------
javafx.stage.Stage stage = new javafx.stage.Stage();
stage.isVisible(true|false);

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Workaround is possible with a lot more code than is necessary. Code size will ultimately collapse due to simplicity.