You can set up certain client as "Inactive" status.
Client profile > Active > turn off "Active customer "
What happens when you set client as "Inactive"?
Inactive client won't be shown on your active (which is default client list) client list.
Inactive client doesn't have pet birthday reminder notification
Inactive client doesn't have rebook reminder notification
You can still search this client, and there will be a "inactive" tag behind the client name.
You can always change client back to active by toggling back to "Active customer".
If you need to block a client from online booking, go to setting > book online > block list to add the client to the "block list".