Não (normalmente).
If a caster takes levels in multiple casting classes, they must select which of those classes’ casting ability modifiers they will use as their casting ability modifier; only one may be applied. Multiple Traditions is an exception to this rule, and may be found in Player Options.
Então você não adiciona dois modificadores de habilidade de elenco, porque você não tem dois modificadores de habilidade de elenco.
If a player or GM wishes a player to follow two traditions (similar to creating a wizard/cleric in traditional Pathfinder), they may do so. When gaining a level in a casting class beyond their 1st, the caster may apply that casting level to a new tradition. They gain an entirely separate set of spheres, talents, caster level, spell points, drawbacks, and boons, which are determined similarly to but completely separate from the first set. When creating a magical effect, they must choose which of these traditions (and its associated spheres, talents, spell points, etc.) they will use; they cannot use aspects of one tradition to empower the other.
Whenever the caster gains a level in a casting class, they must decide which of their traditions that casting class level will be applied to for gaining spell points, casting level, and talents.
Assim, com Múltiplas Tradições, você pode adicionar dois modificadores de habilidade de conjuração (ou até mesmo o mesmo modificador de habilidade duas vezes). Mas isso acontece ao custo de não empilhar níveis de conjurador, não ser capaz de combinar um conjunto de talentos com o outro conjunto e algumas outras restrições minguadas.