I don't have an A99ii but on my other (recent) Sony cameras you go to the DISP setting in one of the cogwheel menus (Page 2 on my A7Rii). Then you choose "Monitor" or "Finder" and for each you can select which options are enabled on the two screens. Then while operating the camera pressing "DISP" (top of the control wheel on the back) cycles through the different selected options, but you need to have the viewfinder active to do this (same for the LCD, it only cycles through the various displays when the LCD screen is active).
So if you never want to see the level indicator you need to uncheck it in the menu(s) as decribed above, if you just want it temporarily out of the way then pressing "DISP" at the top of the control wheel it will cycle to the next option (Graphic display/No Disp. Info/Histogram/Level if these are selected)
Hope this helps, if not just ask and I'll try to explain in a different manner, and I'm not 100% sure it works exactly the same on an A99ii.
