How to set default template for account

I recently discovered that accounts now now contain a setting for the default transaction template to apply when adding a new transaction. My use case would be to define the default payment type for every account so I don't have to add it manually every time. This means that, for example, my bank account would have a payment type of "debit card" while my cash account has "cash".

I opened the Scheduled/template dialog and added template transactions there, where just the payment and account fields are set. Then I went back to the Accounts dialog and wanted to add the default transaction on the Behaviour tab. However, when I open the list box, the only element contained therein is "(none)", i.e. I cannot set the default transaction.

I already tried deleting the account from the transaction template, because I thought that this field might not be set for a default template, but I still cannot select a default template.

How can I use this feature? The user manual has no additional information about this or any restrictions.