The Custom Expression Editor is a tool that allows you to create complex calculations using a syntax called Wrangling Expression Language (WEL). WEL is a domain-specific language that is designed for data manipulation and analysis. WEL supports various operators, functions, and constants that you can use to create custom expressions. You can access the Custom Expression Editor from various places in SAP Analytics Cloud, such as models, stories, datasets, etc. Therefore, the correct answer is Wrangling Expression Language, as it is the language that the Custom Expression Editor uses. Verified Reference:Create Custom Expressions with the Custom Expression Editor