Hi, If you book the GMAT exam at the test center, you does not need to carry anything. The center will provide you everything Such as Scribble book (laminated pages in which you have to solve your answers), black marker, Noise cancellation head phones or ear plugs, Locker key, water, and etc.. You just need to carry your passport and your food items, which you will need for the 8 minute break. Remember: While giving your test, the center people will ask you to remove any jacket or sweater with buttons. So wear proper cloths without any buttons.
They will remove your mask to check anything suspicious, hanker chef is also not allowed (they will give tissues). When you are taking a break, remember to check the time on the wall clock. Come after spending 4 to 5 min because while again coming back they will check you that will take another 1 minute.
Any help Let me know.