client/components/tinymce/plugins/markdown/plugin.js
function markdown( editor ) {
	function allowMarkdownAttribute( event ) {
		const ed = event.target;
		Object.keys( ed.schema.elements ).forEach( function( key ) {
			ed.schema.elements[ key ].attributes.markdown = {};
			ed.schema.elements[ key ].attributesOrder.push( 'markdown' );
		} );
	}

	editor.on( 'preinit', allowMarkdownAttribute );
}
function markdown( editor ) {
	function allowMarkdownAttribute( event ) {
		const ed = event.target;
		Object.keys( ed.schema.elements ).forEach( function( key ) {
			ed.schema.elements[ key ].attributes.markdown = {};
			ed.schema.elements[ key ].attributesOrder.push( 'markdown' );
		} );
	}

	editor.on( 'preinit', allowMarkdownAttribute );
}
function markdown ( editor ) { function allowMarkdownAttribute ( event ) { const ed = event . target ; Object . keys ( ed . schema . elements ) . forEach ( function ( key ) { ed . schema . elements [ key ] . attributes . markdown = { } ; ed . schema . elements [ key ] . attributesOrder . push ( 'markdown' ) ; } ) ; } editor . on ( 'preinit' , allowMarkdownAttribute ) ; }
TinyMCE plugin tweaking Markdown behaviour.

@param {Object} editor TinyMCE editor instance
TinyMCE plugin tweaking Markdown behaviour .