codebase/scss/vendor/_simplemde.scss

//
// SimpleMDE Markdown Editor
//
// Overwrite/Extend styles
// --------------------------------------------------

.CodeMirror-fullscreen,
.editor-toolbar.fullscreen,
.editor-preview-side {
    z-index: $zindex-modal + 2;
}

.editor-preview {
    z-index: $zindex-modal + 1;
}