README.md

Check my neovim config as real life example

return {
  "LintaoAmons/scratch.nvim",
  event = "VeryLazy",
  dependencies = {
    {"ibhagwan/fzf-lua"}, --optional: if you want to use fzf-lua to pick scratch file. Recommended, since it will order the files by modification datetime desc. (require rg)
    {"nvim-telescope/telescope.nvim"}, -- optional: if you want to pick scratch file by telescope
    {"folke/snacks.nvim"}, -- optional: if you want to pick scratch file by snacks picker
    {"stevearc/dressing.nvim"} -- optional: to have the same UI shown in the GIF
  }
  config = function()
    require("scratch").setup({
      scratch_file_dir = vim.fn.stdpath("cache") .. "/scratch.nvim", -- where your scratch files will be put
      window_cmd = "edit", -- 'vsplit' | 'split' | 'edit' | 'tabedit' | 'rightbelow vsplit'
      -- fzf-lua it will order the files by modification datetime desc. (require rg)
      -- snacks.nvim is also supported with files/grep/multi mode toggle and orders by datetime desc. (require rg)
      file_picker = "fzflua", -- "fzflua" | "telescope" | "snacks" | nil
      filetypes = { "lua", "js", "sh", "ts" }, -- you can simply put filetype here
      filetype_details = { -- or, you can have more control here
        json = {}, -- empty table is fine
        ["project-name.md"] = {
          subdir = "project-name" -- group scratch files under specific sub folder
        },
        ["yaml"] = {},
        py = {
          subdir = "python-scripts/%" -- group scratch files under path with random generated subdirectory
          content = { "#!/usr/bin/env python3", "", "" },
          cursor = {
            location = { 3, 0 },
            insert_mode = false,
          },
        },
        go = {
          subdir = true, -- isolate each scratch file in its own subdirectory
          filename = "main", -- the filename of the scratch file in the subdirectory
          content = { "package main", "", "func main() {", "  ", "}" },
          cursor = {
            location = { 4, 2 },
            insert_mode = true,
          },
        },
      },
      localKeys = {
        {
          filenameContains = { "sh" },
          LocalKeys = {
            {
              cmd = "<CMD>RunShellCurrentLine<CR>",
              key = "<C-r>",
              modes = { "n", "i", "v" },
            },
          },
        },
      },
      picker_keys = {
        delete = "<C-x>",      -- key to delete a scratch file from the picker
        toggle_mode = "<C-f>", -- toggle between files/grep/multi (snacks only)
      },
      picker_snacks_multi = false, -- true to start snacks picker in multi mode
      hooks = {
        {
          callback = function()
            vim.api.nvim_buf_set_lines(0, 0, -1, false, { "hello", "world" })
          end,
        },
      },
    })
  end,
  event = "VeryLazy",
}

Modify config at runtime, no need to restart nvim

To check your current configuration, simply type :lua = vim.g.scratch_config

And if you want to modify the config, for example add a new filetype, just call the setup function with your updated config again.

Or you can change the vim.g.scratch_config global variable directly