Hello @Timbo3344, and welcome to the Feedback Group!
With this new editor we retire our Polar markup language, in favor of a standard version of markdown know as CommonMark (https://commonmark.org).
CommonMark, as the original markdown, does not support highlighting, so many standards were born; we made some research and discovered that the currently most used one was the one with
== marker, so we’ve decided to move in that direction.
Said that - when the editor will be inserted inside Bear - all the notes will be automatically translated to the new syntax, so you will not be losing any previous formatting.