Ok, besides python support... The thing I'd like more than anything:

A better way to edit cell with really long function calls.

If nothing else, add color coded parenthesis to the bar at the top and not just in the cell.

Like, sometimes you just need some if/else statements... but try to parse and edit even something fairly simple like:

=IF(AND(LongExpression > 3, Other_longexpression<5),AnotherLongExpression, IF(AND(LongExpression>5,Other_longexpression<10), AnotherLongExpression, 0))

Even with the color-coded parentheses, this is really hard! And God Forbid all those "LongExpression" have a bunch of parenthesis and PEMDAS that needs to be respected.

It's... really goddamn tedious. I lost track of the parenthesis while writing that in this window ...However, if I could just have a little popout window where I could add arbitrary new/lines and spaces, that would make a difficult thing into something downright enjoyable and productive. Something like:

     =IF( 
          AND(
              LongExpression > 3,
              Other_longexpression<5
             ),
          
          AnotherLongExpression, 

          IF(
              AND(
                  LongExpression>5,
                  Other_longexpression<10
                  ),
              AnotherLongExpression,
              0
             )
        )

Would make things much easier to parse.