You can easily rehook and change leash length by using the Collar Ring Menu.
Either:
The Info area tells you:
The top two rows lengthen and shorten the leash ring, by 5m, 1m and 0.5m increments.
The cycle button re-leashes the current leash to the next available collar ring. To cycle to a collar ring that is already occupied, you need to first unleash or re-leash that other ring.
You can also unleash the current leash.
To return to leash options, hit leash….