Allow creation of "incompletely" entered matrices in Spreadsheet View by assuming zeros
When working with sparsely filled matrices (e.g. band matrices or upper triangular matrices), it is currently very cumbersome to enter them in the Spreadsheet View: You have to enter every single number 0 before you can convert it to a matrix. Unless you do that, the "Create Matrix" function is not even selectable, although it is absolutely clear what the user is trying to do:
My suggestion: If you enter some values in the spreadsheet window and then select a rectangular range, allow the user to create a matrix of the corresponding size by assuming 0 for every unfilled cell!