Hi Karthik,

HTML elements like:

<input>
<label>
<select>
<textarea>
<button>
<fieldset>
<legend>
<datalist>
<output>
<option>
<optgroup>
are intentionally not supported by the Editor. The idea of the component is to create rich textual content through a What-You-See-Is-What-You-Get (WYSIWYG) interface. It delivers a set of tools for creating, editing, and formatting text, paragraphs, lists, tables, and other HTML elements. In these lines of words, it could be considered more like an HTML editor. It doesn't intend to serve as a working standalone application and display buttons, inputs, dropdowns, and any other interactive components.

The following Knowledge base article demonstrates how to include a button HTML element inside the Editor, by extending the ProseMirror Plugins and Schema:

https://www.telerik.com/kendo-angular-ui/components/knowledge-base/display-button-inside-editor/

To display inputs, select, or any other unsupported HTML tags the logic should follow the same manner. However such implementation should be considered a developer effort since the Telerik by Progress support service provides guidance and assistance about the built-in API of the Kendo components. 

https://www.telerik.com/account/support-center/scope

The ProseMirror is a third-party library that we didn't provide support for. Since we use the features of the ProseMirror library to create our own component, we decided to expose properties for customizing the underlying schema. Thus the developer can gain full control over the library as well as the Editor component itself. However the ProseMirror has its own API properties and support. That is why any further ProseMirror schema modifications have limited support.

Regards,
Martin
Progress Telerik