Hi Vlad,
What I can suggest is to create a function that will receive the validators and return a combination of the messages that they display. I've created an example to showcase how this can be achieved, enter 'test' to see how both validation messages appear:
https://stackblitz.com/edit/react-multiple-validators?file=app/main.jsx
If you would like to have this as a feature, you can submit a feature request here. We can also do that for you if you prefer us to do it. The feature will be planned based on community interest.
Hope this is helpful.
Regards,
Krissy
Progress Telerik