There’s a very useful putty for watchmakers called Rodico, it can serve this purpose well and can also be stuck to a screwdriver to hold onto the screw while placing it, instead of relying on magnetism (no good in watchmaking to magnetize your screws, I figure cameras are similar, you can increase resistance to movement if magnetism pulls things together…)

I’ve also seen a clever technique of drawing a diagram of whatever you’re working on on cardboard, and stabbing the screw into the cardboard to keep track of where everything lives