How do you manually type in multiple keywords so they are added to an existing keyword hierarchy rather than being concatenated into a new and unwanted keyword?   Is it some sort of delimiter character?

Use either the pipe “|” or the greater than “>” symbol, depending on which way round you want to type:

•  ”|” would be in you want to enter GrandParent | Parent | Child
•  ”>” would be in you want to enter Child > Parent > GrandParent