Even with all the capabilities of the Kolleno RTE, sometimes it's simply easier to copy and paste some sort of existing piece of HTML to use within the editor. The most popular use case for this feature is to re-use existing email signatures and then slightly updating it to use features like Smart Fields.

Note that even though the Kolleno RTE is built on top of standard HTML elements, it does not support all HTML elements due to security restrictions imposed by major email services ie: Gmail and Outlook. Examples of unsupported elements include <button/>, <script /> and <style/>. Where possible Kolleno RTE will try to transform these unsupported elements to a format that is supported.

The HTML source code editor can be found under Format Text -> HTML Source

You can now simply copy-paste your existing HTML source code into the editor and hit save. The Kolleno RTE will proceed to transform the HTML in a way that makes it function within the editor.