Often, the "Unknown" faces will quickly populate, and sometimes lots of unfamiliar faces will appear there. You might not want to delete them right away, since you can ask a relative or friend to help you with their names, but you want to hide them for a while.

An "Ignored" group of faces would solve that situation. All detected faces that you don't want to deal with immediately could go there, and not interfere with the face tagging of faces that you actually know.

A partial solution is currently creating a new dummy person and assign all ignored faces to it, but I am afraid of confusing the face recognizer if I do that.