It is working.

Thank you

ioani

I tried but it did not work.

I managed to solve it. After selecting from menu Window->Floating, Object Explorer tab appeared.

Thanks for your help

The Object Explorer tab is closed not hidden. I closed the Object Explorer tab from X button.

Even though Object Explorer is closed, it should be displayed when F8 is pressed...

This solution doesn't work because values from columns are not ordered except the column that store the timestamp.