You cannot set the webhook in your account by yourself. Please contact our support department and have them set it for you. If you send us the website profile and the webhook in question we will adjust it for you.
We decided to no longer facilitate setting your own webhook because this is an outdated feature. During the preferred implementation of our API, the module itself, in creating the payment, sends along the webhook. This way, the webhook is always up-to-date and no changes have to be made to the account in case of modifications to the webhook.
Nearly all modules use this feature by now. There are just a few modules left where the webhook has to be set by hand.
We received more questions about the entry field than it was ever actually used. Which is why we decided not no show it on the dashboard anymore. Mollie staff can still fill out the webhook.