How do I use Sigma function button then Tab to next cell?

After updating to new Linux Mint 15, LibreOffice no longer lets me automatically sum cells with Sigma button then advance to the next cell using the Tab key. Instead, Tab cycles through objects on the Formula Bar. Is there an option to change the behavior to the “old default?”

Which version of LO are you using?

If I understand correctly you enter values in cells and press Sigma character to sum the column and then to submit formula you press TAB key. When pressing TAB key instead of committing formula and move to next column the selection moves between sigma, cancel, accept buttons. I tested this on v4.0.4 and v4.1.0 and there happening exactly as you described. I actually never used TAB with sigma, always press ENTER, so I don’t know if this was working before. On which version was this working fine?