Metascrolls?
 

How do I apply metamagic effects to scrolls, such as making an Extended Scroll of Summon Monster III, or a three-Metemagic feat scroll of Fireball?

In the list of new Magic items, click "Add custom scroll", then "Click to add a new spell". At the very top of the list of spells is "Custom/Metamagic Spell". Click that to pick a spell and add metamagic to it.

Perfect, thank you.