Q. Can a User Filter include more than one column?
A. No. A User Filter references just one column so that it can then be re-used in other queries and made available in the Column Filter dropdown. You can create multi-column queries but they are Advanced Searches.
Q. Can we ship with our own User Filters?
A. Yes you can. If they are simple expressions then it is straightforward. You can also create dynamic User Filters which contain a predicate that is evaluated at runtime.