nixos-configs/home-manager/neovim/bufferline.lua

require("bufferline").setup {
    options = {
        diagnostics = 'nvim_lsp',
        diagnostics_indicator = function(count, level, diagnostics_dict, context)
            local icon = level:match("error") and " " or " "
            return " " .. icon .. count
        end,
        separator_style = "slant",
        hover = {enabled = true, reveal = {'close'}}
    }
}

vim.keymap.set('n', '<leader>ft', ":BufferLinePick<CR>", {})