Thanks Eric, that seems like a good collection of keystrokes to get me started.

Cheers Andy

see the signatures of all my functions without having to scroll through a whole bunch of code

I know this isn't the same thing, but there is a function for seeing definitions associated with a symbol: Information. There is a special prefix form: ??. So you can evaluate this whenever/wherever you want:

??myFunction

Just using the groupings won't show you the signatures unless you manually keep your header text in sync with the function it relates to, but Information will tell you pretty much everything you want to know.

Thanks, I think I have this working now. However, even though it works, it doesn't seem to do quite what I need. The Cmd ' seems to fold the output cell, but not the input cell. What I am hoping is that there is a way to do something like this.

Given a function such as: myFunction[x_] := Module[ function; function];

I am hoping there is a way to collapse the cell so that it looks like myFunction[x_] ...

That would let me see the signatures of all my functions without having to scroll through a whole bunch of code.

Of course, the sections and sub-sections might be the way to achieve what I am looking for, but perhaps there is something like this built into the notebook interface?

Yes, and Command ' on Mac also works, but what I am struggling with is: 1. It only seems to fold away the result of evaluating a cell 2. It seems as though I need to have the bracket selected for this to work. I.e. just having my cursor on the code doesn't result in the Command ' working. I am wondering if there is a notebook setting that I have to set somewhere. Did this just work out of the box for you?

Thank you both. I am looking for a mouse-less approach, so I will give the sections mechanism.

Cheers Andy

Well, it can be done easily, just not automatically (as far as I know). Use Sections/Subsections/etc and expand/collapse the groups. This is pretty much identical to what IDEs do, but they can parse the text to determine where the blocks are, whereas you'll need to decide for yourself where the folding should happen and manually use the appropriate cell type. This is my standard practice when a notebook starts to feel unwieldy.

I believe there are plugins for Mathematica for other IDEs (e.g. IntelliJ or Atom I think--going on memory here). I suspect the trade-offs are extreme.

I am not aware of any such setting for Cells, and I didn't find anything in the options inspector. But I also may be misunderstanding. How would you edit a cell that only showed the first line (assuming there was stuff in the cell below the fold)? Do you want to be folding/unfolding every time you edit? How should the width of the notebook influence what shows in a folded cell? Is there actually some further objective that you're trying to achieve that you haven't told us about?

Like maybe you want to know where a symbol is defined but you want to hide the definition. You could do this by putting a text cell just before the input cell where the definition is. The text cell could contain the symbol name and you could hide (close) the input cell. Or, better yet, use a cell type that has grouping rules (e.g. Section) instead of a text cell. Then, instead of hiding the input cell, you could just close the group.