Easily finished what I wanted to do!!! The best solution for bulky edition of product description in Shoipify app store. But I have to add the code < br> by myself to change another line instead of typing enter, which may cause difficulties to some users. I don't think many people would try that as me.
A very strange bug is I was charged on 3/21 when I first used it. When I wanted to use it again on 3/23, it charged me again!! Both showed $1.99 every 30 days. What the hell?? Was I double charged???