It is possible to set up crew endorsements per a tail.

When defining a new endorsement (section Settings > Crew Endorsements), click 'Aircraft selection type' to choose between: per a type or per a tail.

Setting up crew endorsements per a tail

By selecting 'per a tail' Leon will show all active tails.

Once a new endorsement's details are added, mark appropriate tail/tails and save changes. On the main list of crew endorsements Leon will show marked tails.