Is your feature request related to a problem? Please describe.
It would be great to be able to customize the error message when submitting an invalid form.

Describe the solution you'd like
A very simple approach e.g. exposing a textfield in the right hand panel editor that allows me to add a custom message either has hard-coded text or JS.

Describe alternatives you've considered
N/A. I can't think of a workaround solution to this. I'm open to suggestions that can work in the interim.

Additional context
N/A