For FileMaker, you can use the new Dialog.SetTextAlignment function to change alignment.
For Xojo, you can use the new SetTextAlignment method in NSAlertMBS class to configure this.
In both cases you can pass left, center and right as desired wish. You can also ask for natural alignment, which may do right or left depending on the locale. Also defined is the justified value, but not sure if the dialog honors it.
You can try those in pr6 of our plugins.