The html email editor offers 3 menu's on the right side of the screen. This article is about other content items.
You can't add a playing video to an email. Most email clients simply don't allow it. But you can add a link to a video. Or an image (still) of the video, or even a short video clip as animated gif. The video box helps to create a thumb of the video and add a play button on top. This is possible for video's hosted on Youtube or Vimeo.
Adding a column is similar as adding another block. Read more about blocks here.
You can add a line to visually divide two sections. The right side panel for divider allows to define color, stroke size and padding.
If you have email fragments available for your sales team, you need to add the email fragment block to the email template as well. This will determine the position in the email where the fragments will be added.
GIFs are a great way to add small animations in your email. You can upload a GIF image using the image box.
If you or your agency has created a specific design that needs additional styling, you can use the HTML box. Add the box and add the html code in the right side panel.