Spoiler: Chest in Vah Naboris Dungeon

Like you, I initially had the thought of "Stasis -> Cut Rope -> Grab with Magnesis", but I found that difficult to pull off, since Magnesis has a projectile (stasis doesn't).

What I found to be easier was to use Magnesis on the chest with the rope still attached, such that it rocked back and forth. During one of the forward swings (when the chest was above the platform), I hit it with Stasis, and only then cut the rope.

This resulted in the chest landing nicely in front of me once stasis wore off. As you yourself found, this chest contains an ancient core.

Shoot the top part of the rope with a fire arrow (do not hit the rope), just the top bit which will then ignite the rope, then the rope will begin to light slowly, Magnesis the chest and when it burns, it's yours.

Alternate method I used after failing the trickshot everyone else mentioned a few times:

Lower the tail, go to the rear-most point of the tail, raise the tail. While the tail is rising, jump off and glide, and aim to land on the platform the chest is hanging from, then use magnesis to catch it while it is still swinging, and pull it up and drag it ALL THE WAY back onto the platform. If the chain is dangling off the edge, it will be enoughto drag the chest off with it. If the chest is all the way back, it will stay put and you can walk up and open it.