Created attachment 112559 [details]
Example of Excel 2010 ALT+ENTER problem

Impossible to successfully open Excel sheets.

Any Excel sheet's cells which contain ALT+ENTER are truncated.  All formula information after the ALT+ENTER is lost.  Any such cells are/can be flagged with an "Err:501"

ALT+ENTER is used to make formulas, especially nested IFs, more readable.  CTRL+ENTER is the LibreOffice equivalent.

At a minimum the ALT+ENTER should not cause the formula to be truncated.  You may lose the readability and put the formula as one long character string, but the formula data must be preserved.  (The preferred solution is to maintain the readability and convert the ALT+ENTER to CTRL+ENTER)

From the attached Excel 2010 sheet, cell BQ8, where <ALT-ENT> represents ALT+ENTER:

=IF(AR8=0,0,<ALT-ENT>
IF(AR8>82,2,<ALT-ENT>
(IF(AR8<51,-1,VLOOKUP(AR8,AdjTbl,3,FALSE)))))

When opened by LibreOffice the cell contains the following single line, which in this case results in an Err:501

=IF(AR8=0,0,)