Table cell alignment can be tricky to restore once someone makes the mistake of changing one row's column width. In my experience it is easiest to simply create a new row above and drag that errant rows contents into the new row and then delete the errant row.

I do this quickly by putting my cursor to the left of the table row above and pressing Enter. Then select the cells in the weird row by clicking and dragging from right to left. Then drag the first cell of the selection into the row above and let go. Then move the mouse to the left of the non-empty errant row so the mouse pointer is a hollow arrow pointing up to the right and click to select that row, right click it and delete.
This only takes a few seconds to perform.

BUT, if you want to fiddle endlessly, you can try dragging the borders individually. Hold the Alt key down as you drag to border to stop it snapping to larger steps and give you fine control over the positioning.

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Andrew Lockton
Chrysalis Design, Melbourne Australia