Does anybody know how to build a dynamic vaadin grid like here: https://cdn.vaadin.com/vaadin-grid/2.0.0-alpha3/demo/data.html#dynamic-height
It is strange because I have never seen that vaadin allow to write code as it is in the link above. Where to put this template? Is it possible that in a standard vaadin code?
This is the demo page for Vaadin Grid Element, not the Grid from Vaadin Framework.
Grid element is a part of so-called Vaadin Elements - set of client-side widgets which can be used from other javascript frameworks (e.g. React, Angular, etc.).
Vaadin released Elements separately from their Framework, so in order to use them from a traditional Vaadin application, you'll need to take additional steps. See this blog post for the detailed walkthrough: Using Vaadin Elements with Vaadin Framework.
You also might want to look through this similar question: Is Vaadin Elements meant to be used with the Vaadin Framework?.