Because there is no "undo" button, recovery relies on logging messages they are deleted. Description Bot Logging
Can see both deleted and edited messages. Cons: Violates Discord's Terms of Service and can lead to account bans. Data Scraping Tools recover-deleted-messages-on-discord
For individual DMs, take screenshots of important conversations as they occur. Because there is no "undo" button, recovery relies
If you need to ensure messages are preserved for evidence or archival: Because there is no "undo" button
Local scripts that cache your own chat history as you use the app.