Custom warning messages for empty fields

Hello, I’ve successfully customized the message that warns a user which is leaving a field empty, following the instructions in the last box at the link

https://calderaforms.com/doc/caldera_forms_field_attributes/

But this method does not work for checkboxes.

The caldera_forms_field_attributes filter seems not to be applied to type checkbox inputs.

I’ve also searched for the string I would like to substitute in localization files, but it seems to be hard coded in a JS file. I guess if I change that value, the standard message will appear newly after the next update.

What should I do in order to achieve the desired result?

Thank you in advance for your help.