Update

public/admin/plugins/tmce/gallery/plugin.js

@@ -0,0 +1,23 @@
+tinymce.PluginManager.add('gallery', function(editor, url) {
+
+    editor.on("BeforeSetContent", function(e){
+        //console.log(e);
+        //e.content = e.content.replace('{{gallery:16}}', '<div class="alert alert-danger">GALERIJA</div>');
+    });
+
+    editor.addButton('gallery', {
+        image: 'data:image/png;base64,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',
+        tooltip: 'Gallery Browser',
+        onclick: open_Browser
+    });
+
+    function open_Browser() {
+        
+        editor.windowManager.open({                
+            title: 'Select Gallery',
+            width: 500,
+            height: 400,
+            url: '/cp/gallery/tmce/plugin'
+        });
+    }
+});