Your TT-1E40F-5 trimmer head is designed with only one side tab, it does not have two tabs.
Please follow the steps:
Press and hold the single side tab all the time.
Keep holding the tab, then turn the outer cover of the trimmer head counterclockwise.
It will loosen and come apart easily. Do not pry or force it by hand.
After you finish restringing the trimmer line, put the cover back and twist it clockwise to lock tightly.
By vevor