Allow cross sheet cell data and formulae
Use data in between sheets, using formula's etc
Werner de Bryun commented
Excel mobile and Excel offline still keeps the formula active when moving between sheets to select your lookup range.
Excel online loses the formula bar forcing the user to write out the formula as a whole. This is far from user friendly - Please fix this urgently
online excel without this utility is useless
Sundeep Kumar commented
From what I could gather by using Excel online, it doesn't allow me to use formulas which reference a cell/row/column from another sheet. For e.g. if I was to use an "index(sheet2A:A,match(sheet1!B2............ A formula like this doesn't work on excel online. It doesn't allow me to convert an offline spreadsheet consisting of such formulas into an online version either. I find this very limiting and quite frustrating.