Here it is explained in more detail with screenshots: https://www.howtogeek.com/198043/how-to-merge-folders-on-mac-os-x-without-losing-all-your-files-seriously

Here it is explained in more detail with screenshots: https://www.howtogeek.com/198043/how-to-merge-folders-on-mac-os-x-without-losing-all-your-files-seriously/ https://www.howtogeek.com/198043/how-to-merge-folders-on-mac... A dialog pops up with 2 choices: Stop or Replace. Replace will delete everything in the destination folder before copying over the source. If you hold the Option key while drag&dropping, you can get one of multiple different pop-up dialogs, depending on the circumstances... and the results are not very predictable.