Doc Variables is not really usable unless you have a lot of time. It is dead slow to add a variable (takes minutes for a simple text variable) and in addition the flow is unclear. Like how can you edit/change a text variable? How can I add it somewhere else in the document. These actions should be clear from the menu but are not.
There are nice features but most of the time but mostly we will use the simple text or drop-down.
For example, once you added a text doc variable you can use it once and then it is gone, nowhere to be found..