List of steps to reproduce (step by step, including full links if applicable):

1. Visit https://zh.m.Wikipedia.org/w/index.php?title=Template:QR/sandbox&uselang=en&preload=Template%3ADocumentation%2Fmirror&summary=%E5%BB%BA%E7%AB%8B%5B%5BTemplate%3AQR%5D%5D%E7%9A%84%E6%B2%99%E7%9B%92%E7%89%88%E6%9C%AC#/editor/all
2. Check the contents of the edit box.

What happens?:

There is nothing in the edit box.

What should have happened instead?:

There is some content in the edit box, which can help you edit well.

Software version (if not a Wikimedia wiki), browser information, screenshots, other information, etc.: