Allow "and"-based dependencies
As it stands, only "or"-based dependencies can be constructed: you can only set a field to be visible if this query is true OR that query is true OR the other query is true.
This proves to be counterintuitive in situations like the following: Suppose I have a task list library. I want the date of a task to be visible only if it's set to actually have a date, since otherwise, the date is just a garbage value. I also want it to be visible only if the task is incomplete, since if the task is complete, then seeing the date thrown in my face nonetheless might cause me undue stress. Therefore, I construct two dependencies for the date: visible when "has date" is checked; visible when "done" is unchecked. Imagine my exasperation when tasks that don't have dates show their dates anyway, just because they're unfinished.