Moisture by the toilet shutoff may be coming from above

Water on the floor near a toilet shutoff doesn’t seem like enough to pin the leak on the supply connection. It could track down from the tank or form as condensation, too.

What clues help tell where it starts? I’d look for moisture returning at a particular joint after the area is dried, but water can travel along the hose or trim before it drips. Is there a useful way to observe the shutoff, hose, and tank connection without loosening anything under pressure? When would a visual check no longer be enough to identify the source?