Yes, you can put whatever you want into each context menu button whether use implement the context menu in GoJS or in HTML.
If you want to invoke context menus on left clicks instead of right clicks, you can override ContextMenuTool.canStart() to check for InputEvent.left instead of InputEvent.right:
myDiagram.toolManager.contextMenuTool.canStart = function() {
var diagram = myDiagram;
if (!diagram.isEnabled) return false;
if (diagram === null) return false;
if (this.isBeyondDragSize()) return false;
if (!diagram.lastInput.left) return false;
return true;
};
But I find this behavior disconcerting.
Also, unless you change the order of tools in the myDiagram.toolManager.mouseUpTools list so that the TextEditingTool comes before the modified ContextMenuTool, the TextEditingTool will never get a chance to run. Read more about tools at: GoJS Tools -- Northwoods Software