I added bar ends to the handlebar, and it really helps with hill-climbing
(see photos attached)
I was able to slide over the grip and brake lever by about 1/2 inch (13 mm) on each side,
far enough to allow mounting the clamp for the bar end.
With bar ends, you can lean your torso farther forward, support more of your weight on your hands to unload the pedal stroke, and get a better body angle to raise your knees. It gives you an alternate hand & wrist position to use when riding longer distances, and also enables a wider grip, which can be helpful for bigger riders.