Create item from scratch?

Hi,

Is there any possiblitity to create a custom item from scratch but not through editing files but in a user interface? I've only found customizing item, but I need to change type of an item sometimes or other things but I can't no matter what base item I choose.

Can I create an item by myself using GUI entirely from start giving it type and so on?

Thank you very much and sorry if I omitted something!