刚查了一下可以透过BTT搭配Apple Script来达到这个目的，方法如下：
Step 1. 在BTT里面把Predefined Action设定成"Run Apple Script in Background"
Step 2. 贴上Apple Script如下：
tell application "System Events"
tell process "SystemUIServer"
tell (menu bar 1's menu bar item 1 whose description is "text input")
click
tell menu 1's menu item "注音"