Extract Text Before Delimiter for multiple columns in a single query step

Select all of the columns you want to transform before applying Transform > Extract > Text.BeforeDelimiter and it should apply the step to all of the selected columns in a single step with M code that looks like this:

= Table.TransformColumns(Source,
      {
          {"Column1", each Text.BeforeDelimiter(_, "|"), type text},
          {"Column2", each Text.BeforeDelimiter(_, "|"), type text},
          {"Column3", each Text.BeforeDelimiter(_, "|"), type text}
      })

If you need to, you can edit each of these transformations separately (like if different columns use different delimiters or need an entirely different transformation).