Yes. You can embed external content using an iframe through the Content Editor's Source Code tool. To access this, select Tools > Source Code from the Content Editor Toolbar within the Custom Content Applet.
The content must come from a secure website using https and the website must be whitelisted in Site Settings.
Add the following code where you want the content to appear:
Replace URL with the web address of the content you want to embed. Where possible, we recommend using the official embed or share code provided by the external website. Please note that some websites do not allow their content to be embedded using iframes.