On https://embeddable.dev.gelinkt-notuleren.lblod.info/
I select the text "hello world" and assign Heading 1
Then press for newline
Select text style "Normal text"
Then "hello world" also changes back to normal text
I would expect "hello world" to keep its heading 1 style and the new line to be normal text.

That is very confusing to people coming from another text editor like e.g. Word.
In other text editors after pressing the text style often automatically changes back to Normal text.