For example, let's say I have a very very long group expression as group parameter. Is it possible to show it in a "text box" so it's easier to read?

The parameter has an option that is called Multi-line String.

alexwheezy
The parameter has an option that is called Multi-line String.

Yes, but it's part of the operator's definition. I can't change it for the built-in nodes.

You can open a text editor to edit the expression. Right click on the parm, in the Expression tab, select Edit Expression/string (or hit Alt+E)

Well yes but that editor isn't like a text box, with wrapping and stuff. So you still have to make it extremely wide or scroll horizontally...

I know one can open in external editors. But, sigh...

By the way this is how multi-line field looks. It doesn't solve my problem: the user still have to scroll horizontally constantly for longer lines.