I can add an event based gateway, but it is added to the project as a Multiple type gateway. When I click on the wrench icon, I see the other options for message, timer, signal, etc. but selecting those adds a new event to the diagram… not change the gateway.
In modeller, if I click on the gateway, I get the set of next flow nodes plus the wrench. If I subsequently click on the wrench, I get the change type of gateway…
If you think your system has a different behaviour, could you post the modeller version and operating system?