现在想要用两个按钮来代替PanelExpanderButton的点击事件，求解决
I really do not understand what you want. It would help if you provided a precise description of what you would like to do plus a screenshot of what you have and other one of what you want.
The complete implementation of “PanelExpanderButton” is provided at https://gojs.net/latest/extensions/Buttons.js.