When using the Microsoft Edge browser with the Editor, you cannot add field values for some form elements. This seems to affect Radio buttons and checkboxes. It is possible that it affects other form elements as well. I also see this same problem when using your demo page https://demos.telerik.com/aspnet-ajax/editor/examples/overview/defaultcs.aspx.

Edge does not offer the hasLayout capability of Internet Explorer, which selects the form element on click. In Edge you can select a form element as you could do it with a text: https://www.screencast.com/t/mo25Rm1kTSdB. The click selection is not currently supported.