It certainly does work as delete. Did you download “gedsplit” and try it?
I have done what you describe as “delete the entire line” a few times on my own tree.
You select a person and the ancestors (or descendants, you choose), then you delete them and save the rest. Then import that back into kiwitrees. The import process deletes your old data, replacing it with the import which does not now include the ones you deleted.
But perhaps that is not what you mean by “delete the entire line”?