Empty slots filled during the day?

[jasin]

During a prepared caster's morning preparations, can they leave slots empty, and then fill them later during the day, like the could in Pathfinder 1E?

[thenobledrake]

No.

[Slamy Mcbiteo]

You cannot leave them open, but a wizard with the Arcane Thesis of Spell Substitution can change a prepared spell given 10 minutes.