Add the following text to Somatic (S) under Components:
“When you cast a spell as an action or a bonus action and you are wielding items in both hands, you may temporarily switch a wielded item to another hand as part of the action or bonus action to complete the Somatic components of a spell. You then return the switched item to the original hand once you complete the action or bonus action. You may not switch a wielded item to a hand that is bound, restricted, or otherwise incapable of wielding items.
If the items you are wielding in your hands are too unwieldy to switch (for example, you are carrying a creature, a large, bulky item other than a weapon that requires two hands to hold, an item over your carrying capacity, etc.), then you are unable to perform the Somatic components of the spell.
You may not switch a wielded item to another hand to complete the Somatic components of a spell cast as a reaction. However, you may choose to drop a wielded item to complete the Somatic component of a spell cast as an action, a bonus action, or a reaction.
For example, Rainblade is wielding a rapier in each hand and wishes to cast Color Spray, a spell with a Somatic component, as an action. To complete the Somatic component of the spell, she can temporarily switch one of her rapiers to the other hand and cast the spell. Once the cast a spell action is complete, she returns the rapier to her hand.
Later, Rainblade attempts to cast Counterspell as a reaction. She cannot complete the Somatic components of the spell because she is wielding a weapon in each hand and attempting to cast the spell as a reaction. Alternatively, she could drop one of her rapiers to complete the Somatic components of the spell.
If you are wielding a two-handed weapon, you may use one of your hands to complete the Somatic components of a spell, even if it is cast as a reaction.
If your physical form provides more than 2 hands capable of performing the Somatic components of a spell, the above rules apply when you are wielding an item in every hand.”