I've been testing various scenarios using Marketo custom objects and would like to share a recent observation: Receiving an "in use" error while trying to delete a custom object.
My custom object was in use by a strange smart list - one that I knew I had not created:
Call me crazy, but this is the icon representing a Smart List:
And when I went to find this mystery list, I received this alert:
Well, the custom object was actually being used... I had forgotten I had created script tokens used during testing. Upon deleting the tokens, I successfully deleted the custom object.
I've submitted a case requesting the icon be changed to help identify being used by tokens using the token icon.