var pluginName = "pluginName";
var pluginGenerator = function (editor) {
	return {
		//...
	};
};
SynapEditor.addPlugin(pluginName, pluginGenerator);

var pluginName = "helloWorldInserter";
var pluginGenerator = function(editor) {
    return {
        buttonDef: {
            label: 'Hello World Inserter',
            iconSVG: `<svg xmlns="http://www.w3.org/2000/svg" version="1.1" viewBox="0 0 16 16">
                        <g xmlns="http://www.w3.org/2000/svg"><title>Layer 1</title>
                            <text stroke="#000000" transform="matrix(0.7835232019424438,0,0,1,0.2672135476022959,0) " xml:space="preserve"
                                    text-anchor="start" font-family="Helvetica, Arial, sans-serif" font-size="13" y="12.580528" x="-1.056391" fill="#000000">HW</text>
                        </g>
                 </svg>`,
            onClickFunc: function () {
                editor.execCommand('insertText', 'Hello World~');
            }
        }
    };
};
 
SynapEditor.addPlugin(pluginName, pluginGenerator);

<!-- synapeditor plugin -->
<script type="text/javascript" src="./plugins/helloWorldInserter.js"></script>

"editor.toolbar": ["bold", "italic", "underline", "strike", "helloWorldInserter"] //helloWorldInserter 플러그인을 툴바 영역에 설정합니다.