FormulaDesk

FormulaDesk adds a variety of additional features to MS Excel 2010, 2013, and 2013. It is designed for engineers, teachers, finance, other professionals to work faster with formulas.

Complex formulas could be visualized and viewed as Math equations. You can also split formula into smaller steps for better understanding.
FormulaDesk can troubleshoot and fix slow Excel files, find slow formulas, trim bloated files, etc. Navigation around Excel is made faster by keeping important parts of your spreadsheets constantly in-view.