How to define variable which should be selected from the list of existing values?

For my IAAS project I need to create a variable to select Azure region for deployment. From UI point of view it should be a dropdown with a list of strings to select one. I’m trying to find how to define a variable this way and the only place I find is Variable Templates (, but I don’t see how to define any! BTW I don’t use Tenants - could it be the cause? Actually yes, I tried to enable Tenants and got Variable Templates menu, but… I don’t need any tenants!

Closing this discussion in favor of another one (I’m going to open) which better conveys what we are trying to achieve.