Hide inactive icons check box in the Task Bar properties down near the bottom in the Notification area? Check that and you should get the arrow back.
I am not sure what happened to my taskbar I think it may have gotten corrupted somehow, but it is missing the collapsible arrow on the right by the clock. I used to have an arrow there to expand my icons as needed but it is missing. I checked the taskbar properties and everything ssems ok but the arrow is missing to expand this area so I am at the whim of the computer
Thank you for your help