'Switch case' won't be much shorter than a bunch of 'ifs'.
Like I said, you can use chooseindex or ternary operators to create objects by name:
Create (a=1 ? "Zombie" : a=2 ? "Goblin" : a=3 ? "Troll" : "Skeleton")
If you need to assign an instance variable you will have to add all these objects to a family and pick last created instance:
Pick Last Created MonstersFamily
MonstersFamily set health to (a=1 ? 5 : a=2 ? 10 : a=3 ? 50 : 3)