Here's a BUYSELL SELLBUY command creation sheet. My guess is Coinshop uses these commands.

https://docs.google.com/spreadsheets/d/1xADbYWdmR58H907fMN78tIl0BykOWhAT9E20L8CfVbc/edit?usp=sharing

The buysell and sellbuy commands are to be used. The > chaining was buggy, and I believe it is disabled these days.
I never used those commands so can't comment on exact use, but trying it out in an otherwise empty market should help see how it behaves.