Yes, you are able to add html from within the landing page editor. This opens up a huge range of capabilities for your landing pages to include forms, maps, javascript snippets and other 'widgets'.

To add an html element, navigate to the 'Add HTML' icon within the landing page editor:

Then, drag the element to your landing page and double-click it to access the html input screen. Input your HTML code into the window provided, and click save to save the html element: