i am using the workaround in this link:
https://forum.obsidian.md/t/a-fix-for-ugly-long-lines-in-fullscreen-v2/1279/21
All the solution will move your scroller from the side to the middle though.
Except this one:
.CodeMirror-lines, .CodeMirror-selected, .markdown-preview-section {
max-width: 700px;
margin: auto;
}
But the .CodeMirror-selected will prevent you from folding heading/indent