In the old composer, after editing a html code you could see directly, if the embed is working and how it looks like. Now, in the new composer after editing, you still see the raw html code. You have to switch on manually to show a preview - then the preview is added, but the html code is still displayed, which is especially disturbing when it's a longer code.
Solution: Switch back to the old UX only see the code when editing it, preview, when not editing.
Hi Simon, this was an intentional change requested by others to reduce unnecessary steps in coming into composer to paste embed codes! We'll keep an eye on this to see if there are other opportunities for how we approach this functionality, but don't have immediate plans to address this at the moment.
See attached screenshots, how it's implemented now, and how it was implemented previously