There isn’t a way to just delete the data from the windows/forms in Extender. The best option I can come up with other than clearing the tables manually or by recreating them in SQL Maintenance is the following.
Copy the Window/Form setup to a new window/form and then delete the original one that has data in it. This will get you the setup of the Window/Form in a new one and then when you delete the old one, it will remove the old setup as well as the data.
You could also export the setup and then delete it and import it again if you want it to have the same ID. The export/import option only does the setup and not any of the data that has been entered.
I am pretty sure you can go to Tools–>Extender–> and delete the entries if they are static entries you have entered. If you are using a lookup where you look up employees, approver, requestor, and etc, then you may have to clear out the table in EXT00101. Let me know if you have further question on or if I did not understand or answer your question correctly. We use extender here at my company as we use both methods and I just had to create a trigger for when someone updates the requestor or approver and send us an email stating what they changes with their credentials, timestamp, Old records, current changed records, and etc.