Would it be useful to be able to organize ones sheets in tab rows? That way you could group together similar sheets - and also not have to scroll back and forth through one long line of tabs, or split your business model up into multiple files.

I.e. you could have your Principal Sheets in one row, and your Auxiliary Sheets (which are used to calculate the underlying assumptions of your principal spreadsheets) in the row below. And then perhaps some totally unrelated ones below that again.

I notice Calc currently allows you to color-code tabs, but I'm not sure how effective that is, as you first have to explain what they mean, plus the color lines aren't all too prominent.