You can optionally define a custom error message in case the validator fails, which will be shown to the user trying to execute the transition.
You have the following options:
Location
Define where the error message should be displayed. Per default the message will be shown at the top of the transition screen, or in case there is no transition screen, as a popup.
Alternatively, you can locate the message below any other field. This option only makes sense, if there is a transition screen defined for the specific transition.
Message
Define the content of the error message in Basic text mode or Advanced text mode.
Translations
After clicking on the Add translation button you can optionally translate the error message to other languages.
The language in which the error message will be displayed depends on the language setting of the individual users.