Unintended deletion of folder. Recovery?

After you confirm the deletion of files and folders, they are deleted immediately.

Depending on the storage location, you might be able to restore them:

If the folder was stored in iCloud Drive, you can restore the files on iCloud.com. See 

https://support.apple.com/guide/icloud/recover-deleted-files-mmae56ea1ca5/icloud 

If the folder was stored in Local Files, the files are saved in device backups (e.g. iCloud device backups). If the folder is very important to you, you might be able to restore it by restoring a device backup.

Other storage locations (cloud storage, Git) might offer other recovery options.