how to add multiple rows on one click of add row link in editable grid?

This should be about as easy as utilizing the standard "add row link" and having it add 2 new entries to the dictionary storing your row data.  Without more detail it's hard to say exactly what you'll need.  What have you tried so far and had difficulty with?

Quick example:

a!localVariables(
  local!rows: {
    {
      name: "row 1",
      id: 1
    }
  },
  
  a!gridLayout(
    headerCells: {
      a!gridLayoutHeaderCell(label: "name")
    },
    rows: a!forEach(
      local!rows,
      a!gridRowLayout(
        contents: {
          a!richTextDisplayField(
            value: fv!item.name
          )
        }
      )
    ),
    addRowLink: a!dynamicLink(
      label: "Add Row(s)",
      saveInto: {
        a!save(
          local!rows,
          append(
            local!rows,
            {
              {
                id: max(local!rows.id) + 1,
                name: "row " & max(local!rows.id) + 1
              },
              {
                id: max(local!rows.id) + 2,
                name: "row " & max(local!rows.id) + 2
              }
            }
          )
        )
      }
    )
  )
)