Position the cursor in the cell to the right of the column break indicated by a vertical line and choose Sheet - Delete Page Break - Column Break. The manual column break is removed.
བརྡ་བཀོད་འདི་འཛུལ་སྤྱོད་འབད་ནི་ལུ...
From the menu bar:
Choose Sheet - Delete Page Break - Column Break.
From the tabbed interface:
On the Layout menu of the Layout tab, choose Column Break.