dnd 5e – Does reapplying Hex cost a spell slot?

The PHB for the spell “Hex” indicates that (5e)

If the target drops to 0 hit points before this spell ends, you can use a bonus action on a subsequent turn of yours to curse a new creature.

Does this mean I am expending another spell slot during my bonus action to curse a new target, or am I simply “commanding” the spell to move? If it doesn’t expend a spell slot, does the duration reset to 1 hour for the new creature, or does the duration apply to when it was initially cast on the first creature?