Playlists and highlighting rules are a different kettle o' fish, since they only have to check a single value (from a tag) against a known list of conditions (equals, less than, starts with etc.).
A virtual tag can consist of any number of functions, in any order, on any number of values.
I can't imagine a GUI design that would cater to more than the simplest examples.
A virtual tag is essentially a mini programming language, so will always require some typing.
Even Visual Studio, with all of Microsoft's resources behind it, is essentially still a text editor after almost 25 years of continuous development.
There are definitely things that could (should?) be done to make it easier to create and edit virtual tags though.
That probably warrants a separate thread, but I'm thinking of things that would be easy to implement, like built-in help text to describe the syntax and use of the different functions with a couple of short examples...
If you get stuck creating your own virtual tags, ask for help on the forum. There are lots of regular forum members (many with ridiculously long and complicated virtual tags) who will help.
Bee excellent to each other...