> You can drag down the bottom of the formula bar/field and make it multi-line

For folks on LibreOffice (currently v24.2):

* There's an downward-pointing "expand" triangle to the far-right of the formula input line.

* That button toggles the formula input area between 1-line vs 6-lines with scrolling.

* Newlines can inserted by shift-enter.

* If there are additional formula lines lines outside the viewable line(s), then a dashed line on the relevant border will be shown. (Plus the regular scrollbar, in expanded mode.)