combine 2 lines in 1 cell into 1 line

CrispLaundry 

Almost the same:

Select the cell or cells in which you want to do this.

Press Control+H or Command+Shift+H to activate the Replace dialog;

Click in the 'Find what' box and press Control+J (I don't know if this works on Mac). It will seem that nothing happens, but you're entering the invisible line break character. Or enter a line break in a cell and copy it, then paste it into the 'Find what' box

Click in the 'Replace with' box and enter a comma followed by a space.

Click 'Replace All'.