How can I convert expression?

You probably want to use the a!keys() function. Here's an example:

a!localVariables(
  local!data: {
    a!map(note: "Sample Note", name: "Sample Name"),
    a!map(note: "Sample Note 2", name: "Sample Name 2"),
  },
  a!gridField(
    data: local!data,
    columns: a!forEach(
      items: a!keys(index(local!data, 1, {})),
      expression: a!gridColumn(
        label: fv!item,
        value: index(fv!row, fv!item, "")
      )
    )
  )
)

However, by using the Keys function I get all of the keys, which I do not want.
Using your example I've added a description key, I do not want that key to be displayed.
In the local!data I also have the primary key value for the record, not too useful fore the end user either.

a!localVariables(
  local!data: {
    a!map(note: "Sample Note", name: "Sample Name", description: "i am a description"),
    a!map(note: "Sample Note 2", name: "Sample Name 2", description: ""),
  },
  a!gridField(
    data: local!data,
    columns: a!forEach(
      items: a!keys(index(local!data, 1, {})),
      expression: a!gridColumn(
        label: fv!item,
        value: index(fv!row, fv!item, "")
      )
    )
  )
)

That's fair, but if you're explicitly choosing certain fields, I think it's easier to just define them yourself. Instead of using a!keys, just put a list with the fields you plan to display.

petel0001 said:

by using the Keys function I get all of the keys, which I do not want.

There was no way of telling this was a constraint from your original post.  Therefore it might be better if you actually talk about your requirements in general, instead of posting a short snippet with no context and expecting us to guess at the details you didn't happen to share originally.

petel0001 said:

by using the Keys function I get all of the keys, which I do not want.

There was no way of telling this was a constraint from your original post.  Therefore it might be better if you actually talk about your requirements in general, instead of posting a short snippet with no context and expecting us to guess at the details you didn't happen to share originally.