My Neovim NvimTree Config

~/.config/nvim/after/plugin/nvim-tree-config.lua

-- Function to set up key mappings 

local function my_on_attach(bufnr)
    local api = require('nvim-tree.api')
    local function opts(desc)
      return { desc = 'nvim-tree: ' .. desc, buffer = bufnr, noremap = true, silent = true, nowait = true }
    end
    vim.keymap.set('n', '<CR>',    api.node.open.edit,                  opts('Open'))
    vim.keymap.set('n', '<Tab>',   api.node.open.preview,               opts('Open Preview'))
    vim.keymap.set('n', '<C-v>',   api.node.open.vertical,              opts('Open: Vertical Split'))
    vim.keymap.set('n', '<C-x>',   api.node.open.horizontal,            opts('Open: Horizontal Split'))
    vim.keymap.set('n', 'a',       api.fs.create,                       opts('Create File Or Directory'))
    vim.keymap.set('n', 'c',       api.fs.copy.node,                    opts('Copy'))
    vim.keymap.set('n', 'g',       api.tree.change_root_to_node,        opts('CD'))
    vim.keymap.set('n', 'i',       api.node.show_info_popup,            opts('Info'))
    vim.keymap.set('n', 'm',       api.marks.toggle,                    opts('Toggle Bookmark'))
    vim.keymap.set('n', 'p',       api.fs.paste,                        opts('Paste'))
    vim.keymap.set('n', 'P',       api.node.navigate.parent,            opts('Parent Directory'))
    vim.keymap.set('n', 'r',       api.fs.rename,                       opts('Rename'))
    vim.keymap.set('n', 't',       api.marks.bulk.trash,                opts('Trash Bookmarked'))
    vim.keymap.set('n', 'x',       api.fs.cut,                          opts('Cut'))
    vim.keymap.set('n', '<2-LeftMouse>',  api.node.open.edit,           opts('Open'))
end


-- Call function to set up key mappings
-- and turn off git icons

require("nvim-tree").setup({
  on_attach = my_on_attach,
  view = {
    side = "right"
  },
  renderer = {
    icons = {
      show = {
        git = false
      }
    }
  }
})


-- Automatcially open nvim-tree on startup 
-- then switch to main buffer

local function open_nvim_tree()
  require("nvim-tree.api").tree.open()
  vim.cmd.wincmd 'p'
end

vim.api.nvim_create_autocmd({ "VimEnter" }, { callback = open_nvim_tree })


-- Set up to toggle back and forth to nvim-tree
-- and the current buffer
local function toggle_nvimtree()
  if vim.fn.bufname():match 'NvimTree_' then
    vim.cmd.wincmd 'p'
  else
    vim.cmd('NvimTreeOpen')
  end
end

-- Toggle to File Explorer Key Mapping
vim.keymap.set('n', '<M-E>',  toggle_nvimtree, {})

-- Save and close a buffer ending up on the previous
-- buffer or in a new buffer
vim.keymap.set('n', '<M-W>', ":w<bar>:bp<bar>sp<bar>bn<bar>bd<cr>", { desc = 'Close buffer' })
vim.keymap.set('i', '<M-W>', "<ESC>:w<bar>:bp<bar>sp<bar>bn<bar>bd<cr>", { desc = 'Close buffer' })


-- Save and quit out of neovim including closing 
-- nvim-tree
vim.keymap.set('n', '<M-Q>', ":wqa<cr>:bd<cr>", { desc = 'Save and quit' })
vim.keymap.set('i', '<M-Q>', "<ESC>:wqa<cr>:bd<cr>", { desc = 'Save and quit' })

Notes

Help via: `:h nvim-tree-setup``
This set up turns off the git icons in the tree. I find them more distracting that useful

Default Key Mappings

These are the default key mappings you can pull it for easy reference:

-- BEGIN_DEFAULT_ON_ATTACH
  vim.keymap.set('n', '<C-]>',   api.tree.change_root_to_node,        opts('CD'))
  vim.keymap.set('n', '<C-e>',   api.node.open.replace_tree_buffer,   opts('Open: In Place'))
  vim.keymap.set('n', '<C-k>',   api.node.show_info_popup,            opts('Info'))
  vim.keymap.set('n', '<C-r>',   api.fs.rename_sub,                   opts('Rename: Omit Filename'))
  vim.keymap.set('n', '<C-t>',   api.node.open.tab,                   opts('Open: New Tab'))
  vim.keymap.set('n', '<C-v>',   api.node.open.vertical,              opts('Open: Vertical Split'))
  vim.keymap.set('n', '<C-x>',   api.node.open.horizontal,            opts('Open: Horizontal Split'))
  vim.keymap.set('n', '<BS>',    api.node.navigate.parent_close,      opts('Close Directory'))
  vim.keymap.set('n', '<CR>',    api.node.open.edit,                  opts('Open'))
  vim.keymap.set('n', '<Tab>',   api.node.open.preview,               opts('Open Preview'))
  vim.keymap.set('n', '>',       api.node.navigate.sibling.next,      opts('Next Sibling'))
  vim.keymap.set('n', '<',       api.node.navigate.sibling.prev,      opts('Previous Sibling'))
  vim.keymap.set('n', '.',       api.node.run.cmd,                    opts('Run Command'))
  vim.keymap.set('n', '-',       api.tree.change_root_to_parent,      opts('Up'))
  vim.keymap.set('n', 'a',       api.fs.create,                       opts('Create File Or Directory'))
  vim.keymap.set('n', 'bd',      api.marks.bulk.delete,               opts('Delete Bookmarked'))
  vim.keymap.set('n', 'bt',      api.marks.bulk.trash,                opts('Trash Bookmarked'))
  vim.keymap.set('n', 'bmv',     api.marks.bulk.move,                 opts('Move Bookmarked'))
  vim.keymap.set('n', 'B',       api.tree.toggle_no_buffer_filter,    opts('Toggle Filter: No Buffer'))
  vim.keymap.set('n', 'c',       api.fs.copy.node,                    opts('Copy'))
  vim.keymap.set('n', 'C',       api.tree.toggle_git_clean_filter,    opts('Toggle Filter: Git Clean'))
  vim.keymap.set('n', '[c',      api.node.navigate.git.prev,          opts('Prev Git'))
  vim.keymap.set('n', ']c',      api.node.navigate.git.next,          opts('Next Git'))
  vim.keymap.set('n', 'd',       api.fs.remove,                       opts('Delete'))
  vim.keymap.set('n', 'D',       api.fs.trash,                        opts('Trash'))
  vim.keymap.set('n', 'E',       api.tree.expand_all,                 opts('Expand All'))
  vim.keymap.set('n', 'e',       api.fs.rename_basename,              opts('Rename: Basename'))
  vim.keymap.set('n', ']e',      api.node.navigate.diagnostics.next,  opts('Next Diagnostic'))
  vim.keymap.set('n', '[e',      api.node.navigate.diagnostics.prev,  opts('Prev Diagnostic'))
  vim.keymap.set('n', 'F',       api.live_filter.clear,               opts('Live Filter: Clear'))
  vim.keymap.set('n', 'f',       api.live_filter.start,               opts('Live Filter: Start'))
  vim.keymap.set('n', 'g?',      api.tree.toggle_help,                opts('Help'))
  vim.keymap.set('n', 'gy',      api.fs.copy.absolute_path,           opts('Copy Absolute Path'))
  vim.keymap.set('n', 'H',       api.tree.toggle_hidden_filter,       opts('Toggle Filter: Dotfiles'))
  vim.keymap.set('n', 'I',       api.tree.toggle_gitignore_filter,    opts('Toggle Filter: Git Ignore'))
  vim.keymap.set('n', 'J',       api.node.navigate.sibling.last,      opts('Last Sibling'))
  vim.keymap.set('n', 'K',       api.node.navigate.sibling.first,     opts('First Sibling'))
  vim.keymap.set('n', 'L',       api.node.open.toggle_group_empty,    opts('Toggle Group Empty'))
  vim.keymap.set('n', 'M',       api.tree.toggle_no_bookmark_filter,  opts('Toggle Filter: No Bookmark'))
  vim.keymap.set('n', 'm',       api.marks.toggle,                    opts('Toggle Bookmark'))
  vim.keymap.set('n', 'o',       api.node.open.edit,                  opts('Open'))
  vim.keymap.set('n', 'O',       api.node.open.no_window_picker,      opts('Open: No Window Picker'))
  vim.keymap.set('n', 'p',       api.fs.paste,                        opts('Paste'))
  vim.keymap.set('n', 'P',       api.node.navigate.parent,            opts('Parent Directory'))
  vim.keymap.set('n', 'q',       api.tree.close,                      opts('Close'))
  vim.keymap.set('n', 'r',       api.fs.rename,                       opts('Rename'))
  vim.keymap.set('n', 'R',       api.tree.reload,                     opts('Refresh'))
  vim.keymap.set('n', 's',       api.node.run.system,                 opts('Run System'))
  vim.keymap.set('n', 'S',       api.tree.search_node,                opts('Search'))
  vim.keymap.set('n', 'u',       api.fs.rename_full,                  opts('Rename: Full Path'))
  vim.keymap.set('n', 'U',       api.tree.toggle_custom_filter,       opts('Toggle Filter: Hidden'))
  vim.keymap.set('n', 'W',       api.tree.collapse_all,               opts('Collapse'))
  vim.keymap.set('n', 'x',       api.fs.cut,                          opts('Cut'))
  vim.keymap.set('n', 'y',       api.fs.copy.filename,                opts('Copy Name'))
  vim.keymap.set('n', 'Y',       api.fs.copy.relative_path,           opts('Copy Relative Path'))
  vim.keymap.set('n', '<2-LeftMouse>',  api.node.open.edit,           opts('Open'))
  vim.keymap.set('n', '<2-RightMouse>', api.tree.change_root_to_node, opts('CD'))
  -- END_DEFAULT_ON_ATTACH

References

This is where I got the toggle function from