CI/CD Variable can't contain special character - UI improvement proposal

Hi!

If I try to create a CI/CD variable with disallowed character (for example, 'SSL.CRT'), I got an error with the description only after clicking the "Add Variable" button. The dialog with the content of the CI/CD variable is disposed and I return to the list of CI/CD variables with an error:

It will be great improvement if the validation won't close the "Add variable" dialog. And I will see instantly the message stating the allowed subset of characters for "Key" field (=the name of variable). Probably it is good idea to implement javascript filter disallowing entering the incorrect symbols into "Key" field.