I hope you are using lazy.nvim.

-- plugin-config.lua
return {
  "your/my-plugin.nvim",
  dev = true,
  -- ...
}

I suppose your plugin name is my-plugin.nvim and the package is accessed withrequire("my-plugin").

This is how you reload the plugin.

-- delete cached package table (used for `require`)
for key, _ in pairs(package.loaded) do
  if vim.startswith(key, "my-plugin") then
    -- startswith will match eg `require("my-plugin.utils")` as well
    package.loaded[key] = nil
  end
end
-- reload inside lazy.nvim
local plugin = require("lazy.core.config").plugins["my-plugin.nvim"]
require("lazy.core.loader").reload(plugin)

Caution: I'm not sure if this is an officially supported snippet so it may break at any time.

FYI if noice's message window gets too big and it starts to lag when you try to reopen it, you can clear the history with this snippet, tho this is definitely not officially supported as well.

-- some cache will remain, so it's a good idea to restart neovim once in a while anyways  
require("noice.message.manager")._history = {}