The data model used in Lead Time setup in the tracking control center doesn't make sense.

Lead time is in reality a combination of Leg and Activity.

That would allow for the use of generic activities set up with unique lead times in combination with a specific leg.

Ie:

It takes 4 days to load a container in China but only 2 days to load a container in India.

It takes one day to clear a shipment in Amsterdam but 5 days in Havanna.

As it is in F&O, you would need to create a new activity for each possible leg to be able to capture a lead time for that particular journey.