Can an alias category combine two other categories?

[BanjoTom]

I know how to create the very useful "alias" categories.  But is there a way to make an alias category that aliases two separate categories?  That is, is there any sort of "AND" syntax that can be put into the "Is Alias of" property of a category to make it an alias of TWO individual categories? 

[Mario]

No. An Alias is always mapped 1:1 for another category.

You can virtually combine multiple categories into one category using a category formula. This won't allow for assignments, but you have a permanent view of the combined contents of all categories you use in the formula.

A category splasher favorite allows you to assign (or remove) files to/from multiple categories.