how to see onion skin with Open GL turned off?

I cannot see my onion skin with the Open GL off…I can see it fine when its on…how can I changet this so that I dont have to go back and forth?
thank you

Normally, you would can see the onion skin in both, in or off OpenGL mode, in order to see or not the real time antialiasing. (OpenGL preferences option).
Regarding select the layer that you are working on, in camera view or drawing view, and enabled the Show Onion Skin tools button. In camera view, with OpenGL view button enabled, NOT in render view, (the right side button). In drawing mode, you need select in timeline or x-sheet, the drawing cell in use, and, in all cases open the blue brackets on top the red cursor head in order to show a selectable range of frames affected to the onion skin feature.
All this, working on pure drawings, if you use symbols, you would work into the symbol to access the drawings, and so, can see the onion skin if you work in drawing mode. Hope that helps.