-- global for icons

vim.g.my_icons = {
  ...
  fileformat = {
    unix = '',
    dos = '󰨡',
    mac = '󰀷',
  },
  diagnostics = {
    error = ' ',
    warn = ' ',
    hint = ' ',
    info = ' ',
  },
  ...
}

-- within lualine config
...
    {
      'diagnostics',
      symbols = vim.g.my_icons.diagnostics,
    }
...
    {
      'fileformat',
      symbols = vim.g.my_icons.fileformat,
    }
...

    options = {
      -- new key
      -- NOTE: defining values here can be overwritten if they were also defined under their respective sections,
      -- having empty value means defaults are applied.
      icons = {
        -- each key is named after its section.
        fileformat = {}
        -- and follows the rules of its section.
        lsp_status = {
          icon = '',
          symbols = {
            spinner = { '⠋', '⠙', '⠹', '⠸', '⠼', '⠴', '⠦', '⠧', '⠇', '⠏' },
            done = '✓',
            separator = ' ',
          },
        }
      }
    }