usr338 You can, via frontend functions running before record save. But you would likely need to call the backend to check dependencies to catch these kinds of errors.
Errors resulting because of a "NO ACTION" configuration in relationship attributes can often be avoided by good app design. Usually you would want to avoid users deleting still referenced records (if that does not matter, you could choose "CASCADE" and there would not be an error) - if you design your app in such a way that referenced records show what they are referenced by (by showing lists in relevant forms) or by being only visible as sub-records (if there is such hierarchy), it becomes very clear what can and really should not be deleted.
Of course this is not always possible and the system must block these kinds of deletion attempts when they occur and relationship would break. There could be a possible solution where an author could design custom error messages for specific relationships (without backend functions) - but this soluation would need to work in a multi-language environment. I´ll add it to our list - maybe there is something that can be done.
