A search pattern used with
/, entered on the vim command line,
can be very complex.
But even for a normal regular expression pattern, syntax highlight of the expression syntax would be helpful.
The pattern syntax in
vim provides a large number of special pattern atoms. Some of them use multiple characters.
I do need to look them up to use them - that's easy.
The harder part is to continue editing the pattern, because it can become hard to read quickly.
I think even a very simple kind of syntax highlight for the pattern input would be helpful, like three colors for text, standard pattern atoms and special pattern atoms.
It would help users new to writing nontrivial patterns a lot - and also, it would help experienced users, new to writing even more advanced patterns, just the same way.