The Tome of Peritia allows you to safely store your experience.
pressing [Shift] and [ПКМ] with the Tome in hand stores one level of XP. Pressing [ПКМ] retrieves a level. Hold [ПКМ] to store/retrieve multiple levels.
As you have the Curios API installed, you can equip the Tome of Peritia as a charm. If you want to wear more curios at once, consider using a Sigil of Holding, or the Socketed Upgrade for your Living Armour.