Custom HLSL code in Material Function Editor

So I’m trying to write my own shader code in a custom node in the material function editor like this:

But I don’t see a way to expand the code text field. What am I missing?

I’ve also posted the question to the AnswerHub:

Has anyone had any luck using the custom material expression nodes?

I remember putting in a request to have this fixed late last year - you cannot expand it.

I have to do my stuff in notepad and paste it in.

Well that sucks. Maybe it’s not a priority since the documentation says doing it this way decreases performance.

Anyway, thanks for taking the time to respond.