My only thought when I read the question was if there can there be a webhook or a button to delete those time entries. ie i agree that there is not a way to prevent them from being created, but maybe they can be quickly deleted.
The Webhook could fire when a record was created and the name of the Parent starts with "Copy of", because Quick Base always renames that designated field to be called Copy of .... or else you make a button that is displayed to the user when the Parent is named "Copy of ..." and ghere are still Time Card Entries and have that button be a URL formula to delete those Time Entries.
