Anchor onion skin markers

Hello, I’d love to be able to anchor the onion skin start and end points. This would make it incredibly helpful to work on the trajectory of an arc across a specific set of frames. For example, if I were adjusting the arc of a ball in space from frames 1 - 10. I could anchor the onion skin markers and see the whole arc without the playhead moving the onion skin. As it functions now, if I go to work on frame 7 out of 10 the onion skin moves beyond what I want to see and I have to adjust the start and end points, which totally disrupts the workflow. Hope that made sense, and thank you!