Pathfinder (like other 3.x rules) has Specialist Wizards, who adopt particular Schools of Arcane Spells.
The Specialist School (like a Cleric's Domain spells) are the only occupants for certain special spell slots;
Forbidden School spells take 2 slots, and are harder to learn, enchant, ...
Without asking PCGen to actually implement limiting where spells are allocated, it would be really useful if the UI highlighted them (much like the highlight of non-proficient weapons).
Then i could avoid the mistake of populating a Wizard with many forbidden spells, and make easy the task of ensuring the specialist slots are properly occupied.
Pathfinder core set