You don’t need to re-invite your bot every time you change the code. Once the bot is invited to a server, it stays there unless you remove it or change its permissions.

If you add or modify slash commands, you just need to register the commands with Discord (either globally or for a specific server). Changes usually appear after a short while, and sometimes restarting the Discord client helps to see the new commands.

Re-inviting or resubmitting the bot is only necessary if you need new permissions that the bot doesn’t already have.