Line break in a single paragraph with a \ (backslash) at the end of the line is removed automatically on every save.
The preview of the extension still shows there is a line break but vscode's original preview and gitlab's preview shows no line break.
I think the expected behavior to keep the backslash at the end of the line and only show line break in the preview if it has this backslash.
Thank you for help and for the development!