Thread: Any way to display all categories in the post an ad section?

Any way to display all categories in the post an ad section?

I am looking for a way to display all the categories in the post an ad section, just like kijiji.com when you press post an add, a big page pops out and displays every categories. So no need to select the primary parent category and then select the subcategory. Is there any way I could achieve that function? Any plugin or child theme I could use? Thank you so much for your help!