React Form - Customize a Validation Icon

To customize the validation icon, modify the dx-texteditor-input-container class. To shift the icon's position to the left, apply these CSS rules:

CSS
.dx-texteditor.dx-invalid .dx-texteditor-input-container::after {
    left: 4px;
    right: 0;
}

.dx-texteditor.dx-invalid .dx-texteditor-input {
    padding-right: 0;
    padding-left: 34px;
}

Examine CSS if further customization is required.