public static enum ModalityLevel {
        STRONG("strong", "modality-strong"),
        LIGHT("light", "modality-light center-vertical"),
        NON_MODAL("non-modal", "modality-non-modal");
}

When one defines a dialogDefinition with modalityLevel and set it to 'NON-MODAL', our system doesn't pick up the correct enum constant for that, simply because we check for the info.magnolia.ui.api.overlay.OverlayLayer.ModalityLevel#getName() method . However, If user tries to define it as 'NON_MODAL' which is the constant value, then system will not pick it up because info.magnolia.ui.api.overlay.OverlayLayer.ModalityLevel#getName() method is not able to find it and our configuration sources is not complaining about it at this time.

So to sum up:

• Define as 'non_modal' -> dialog doesn't work but configuration sources do not complain.
• Define as 'non-modal' -> dialog works but configuration sources complain.

FYI: It's also reproducible in JCR

A quick solution could be to simply have those values equal.

Quick Dialog Definition:

modalityLevel: non_modal
form:
  tabs:
    - name: tabText
      label: Text
      fields:
        - name: title
          class: info.magnolia.ui.form.field.definition.TextFieldDefinition
          label: Title
actions:
  commit:
    class: info.magnolia.ui.admincentral.dialog.action.SaveDialogActionDefinition
    label: Save
  cancel:
    class: info.magnolia.ui.admincentral.dialog.action.CancelDialogActionDefinition
    label: Cancel